OROVILLE, Wash. (AP) - Darrel Williams and Steve Kartchner sit silently in their saddles on a recent August day, resting the mustangs that just carried them up a bluff overlooking Lake Osoyoos.

Beside them and behind them, a four-strand barbed-wire fence - the international border - stretches off into the distance of sagebrush and bunchgrass across rocky, rolling and sometimes steep ground.

In front of them, a near-vertical cliff drops down to green orchards, pastures and yards next to the mile-wide lake. Across the water, the land climbs again through farms and dryland to the 7,800-foot Chopaka Mountain and more tall peaks in the Pasayten Wilderness beyond.

Breathtaking, yes. But Williams and Kartchner are not here to take in the view.

They are mounted U.S. Border Patrol agents, and they're looking for signs of illegal crossings - footprints or flattened grass - along their 80-mile section of the 4,000-mile border with Canada.

And they are two of the first in the nation to do this work on wild mustangs -- adopted from the Bureau of Land Management, broken by inmates in Colorado, and still being trained by these Border Patrol wranglers in the backcountry of Okanogan County.

Project Noble Mustang, launched this summer, is designed to save taxpayer money while showcasing the mustang. "To be able to put them to work protecting America just makes you grin," says Richard Graham, agent in charge of the agency's Oroville station.

Horses were an important part of the U.S. Border Patrol when the agency was created in 1924. Agents then were expected to have their own horse and tack, and the government paid for feed.

But as the agency started patrolling in vehicles, the use of horses declined, particularly along the "friendly" northern border with Canada.

Steven Garrett, assistant chief for the agency's Spokane Sector, says the Border Patrol relies on sophisticated technology. The sector is about 300 miles long and runs from the North Cascade Mountains in Okanogan County to the Rockies in Montana.

They have four new boats, a helicopter and a fixed-wing airplane and several ATVs. Hidden in the woods and at crossings are remote cameras and all kinds of sensors to detect movement, footsteps, heat and metal.

"We want everyone to think that even if a squirrel crosses, we'll know it," he says.

The most recent "vehicle" to rejoin the list in his sector is the horse.

Garrett says it's difficult to compare the costs or effectiveness of horses with other modes of transportation.

"At the end of the day, it really doesn't matter, because we need the best tool for the job. In some places, there really are no other choices. We either walk or use horses," he says.

No one's quite sure how long it's been since the Border Patrol used horses along the Canadian border.

But their comeback started just a few years ago, when two stations in the Spokane Sector started leasing horses to patrol areas where vehicles can't go.

Last year, each of the sector's seven units got $25,000 to contract for horses, which cost about $150 per horse per day, says Border Patrol spokeswoman Danielle Suarez in Spokane.

This year, the Spokane sector adopted eight mustangs, and bought two packing mules.

Four of the mustangs went to the Border Patrol station in Whitefish, Mont., which patrols Glacier National Park.

The other four, and the two mules, are stationed at Oroville.

Graham, who's in charge of the Oroville station, couldn't be happier.

In 1999, he says, "I bought my own horse, and they let me go in the parade to keep me quiet."

At the time, Oroville's Border Patrol agents traveled throughout Okanogan County, sometimes raiding fruit packing houses as far south as Brewster to catch illegal workers, he says.

But after the terrorist attacks on Sept. 11, 2001, their focus shifted north, to the border, Graham says.

That change, plus a doubling in the number of agents stationed at Oroville, brought a dramatic increase in arrests of both drug smugglers and illegal immigrants caught crossing the border.

But it's not the drug smugglers they're after.

Their eyes stay fixed on the border to keep out terrorists and weapons of mass destruction, he says. He and his agents take that responsibility very seriously, even personally, he says.

"We know they smuggle people. And they smuggle narcotics and weapons, cigarettes and booze. And if you can smuggle in people and narcotics successfully, what are your limitations? Who is this person they're smuggling? What's in that bag? That's what's given us a different perspective since 9-11. Aliens were always our game. Now, that doesn't interest us as much," Graham says.

When the job turned to shutting down illegal entries, Graham's job got tougher.

Fifty of the 80 miles of border that he covers - from the Pacific Crest Trail to just inside Okanogan County's border with Ferry County - are in wilderness, where there are no roads, and where ATVs, snowmobiles and other motorized vehicles are prohibited.

Five years ago, Graham started contracting with Frontier Ranches in Oroville, which provided ready-to-use horses on a by-the-day basis.

Now that the entire sector - the only region using horses along the border with Canada - is tuned in to the idea, Graham expects he'll start to see horse patrols pop up at other northern Border Patrol units, "from Blaine to Maine."

The advantages of patrolling on horseback are many, Garrett says. "No. 1, they're very quiet. You can sneak up on people, and they're not going to know you're coming," he says.

Also, they'll alert you when someone's near.

"I did ride horses on the southern border, and it was amazing how the horse's head would suddenly spring up and their ears would go up when someone was coming. They can hear better than we can," he says.

Garrett says horses have already proven their worth. "Our horse patrols on the southern border are out there catching people every day," he says.

But up here in the north, he won't be judging their effectiveness by the number of people that agents on horseback arrest.

"The question is, were you out there effectively patrolling the area? If not, and you are now, that's a good measure of your effectiveness," he says.

Graham says his horse patrol agents, while on horseback, have not yet caught anyone crossing illegally. But when they are out there in the right place at the right time, he has little doubt they'll be able to run them down.

"You can't outrun a horse. And if you're on another horse, it's a matter of whether you can outrun Darrel," he smiles.

For the most part, Graham says, agents on horseback are out there gathering intelligence.

They look for signs of recent crossings and look to the sky for low-flying aircraft.

Now that his agents have their own mustangs, he's been sending them into the Pasayten Wilderness on trips that last a week to ten days.

"Most of July we had six to 12 horses out there the whole month," he says.

U.S. Attorney Jim McDevitt went into the Pasayten Wilderness with the mounted Border Patrol in mid-July to see, firsthand, what they do.

McDevitt is the top federal prosecutor for the Eastern Washington District, based in Spokane. He also serves on an international team that sets policy for 15 international border enforcement teams across the country.

He raised concerns two years ago that large sections of the border - all along the Pasayten Wilderness and North Cascades National Park - were difficult, if not impossible, to patrol.

These areas, he says, need watching. "Anyone who thinks Eastern Washington is a sleepy section has got their head in the sand," he says.

McDevitt says he sees the horse patrols as a much-needed supplement to cameras and sensors.

"It let's people know it's a hit-or-miss deal as to whether or not they're going to run into a horse patrol," he says. "If you know there are random patrols coming through an area, that's going to change your whole thinking," he says.

The patrols in the wilderness will also help agents build rapport with local residents, and the visitors who use the backcountry, he says.

"They cultivate sources, and people realize they aren't a bunch of jack-booted thugs kicking in doors," he says, adding, "You'd be surprised how many citizen tips we get."

To the agents in the field, the advantages of being on horseback are obvious.

While resting the mustangs on that bluff east of Lake Osoyoos, Graham, Williams and Kartchner talk about this vantage point.

"If we want to watch the lake, we could ride up here and have the whole thing covered," Williams says. "The regular boat can hide, and they'd think we're not there."

Then they can radio their counterparts on the lake if someone tries to sneak across, Kartchner adds.

They talk about using night goggles and infrared scopes.

Graham says even if they lined the border with cameras and sensors, it would do little good without a patrol agent in the field to catch them after they cross.

He looks down at an orchard that straddles the two countries - a fence separating the two orchards, but barely an open space between fruit trees on both sides of the border.

It would take only seconds for someone to sneak across that before they're under the cover of trees again, he notes.

"But up here, you can see. And they've got to come out (of the orchard) again," he says.