Similarly, Canadians will also have to present a passport to enter the United States, said the officials, who spoke on condition of anonymity. Canadians have been the only foreigners allowed to enter the United States with just a driver's license.

An announcement, expected later Tuesday at the State Department, will specify that a passport or another valid travel document will have to be shown by U.S. citizens, the officials said.

These include a document called Sentri that is used for Mexico travel or a Nexus for Canada travel.

Until now, Americans returning home from Canada have needed only to show a driver's license or other government-issued photo identification card.

Americans returning from Mexico, Panama or Bermuda currently need only a government-issued photo identification card plus proof of U.S. citizenship like an original birth or naturalization certificate, according to the State Department's Web site.

The new rules, to be phased in by Jan. 1, 2008, were called for in intelligence legislation approved last year by Congress.

Safeguarding U.S. borders are a top concern of U.S. intelligence and security officials. The concern increased after the Sept. 11, 2001, terror attacks on the World Trade Center in New York and on the Pentagon.

The travel industry has raised concerns that the changes might hamper tourism, one official said.

The announcement follows a three-way summit last month that President Bush held with Prime Minister Paul Martin of Canada and President Vicente Fox of Mexico.

Speaking at Baylor University at Waco, Tex., Bush said border controls with Mexico had to be tightened to make sure that terrorists, drug runners, gun runners and smugglers do not enter the United States.

Besides a passport, re-entering Americans could use another approved travel document like frequent travel cards, which are issued to some people who travel often between the U.S. and Mexico. These cards typically are used to avoid long border-crossing lines.

But in most cases, only passports will do, another U.S. official said.

The new system will deal first with the Caribbean, then Mexico and Canada. It will start at airports and subsequently spread to land crossings, said an official speaking on condition of anonymity.

U.S. inspectors will bear less of a burden with the changes because they won't have to sift through different kinds of travel documents, the officials said.