President Bush, rebuffing international criticism of a secret U.S. prison system abroad for terrorism suspects, said today he will continue to "aggressively pursue" terrorists and insisted that "any activity we conduct" in that effort is lawful and does not include torture.

Concluding a four-day trip to Latin America with a stop in Panama, Bush also said his administration was close to an agreement with Panama on a bilateral free-trade accord. But he criticized Democrats in Congress on the issue, accusing them of backing away from the party's traditional support for free-trade agreements.

In a news conference with Panamanian President Martin Torrijos in Panama City, Bush was queried about an "international outcry" over a secret CIA prison system that has included sites in eight countries, including several democracies in Eastern Europe. After The Washington Post disclosed the system last week, the International Committee of the Red Cross, the European Union and human rights groups demanded information about the prisons, and an E.U. spokesman said their existence could violate international law.

Asked whether he would allow the Red Cross to have access to the prisoners and whether he agreed with Vice President Cheney that the CIA should be exempt from legislation to ban torture, Bush did not answer directly. Nor did he confirm the existence of the secret prisons. Instead, he launched into a strong defense of the U.S. war on terrorism.

"Our country is at war, and our government has the obligation to protect the American people," Bush said emphatically. "And we are aggressively doing that. We are finding terrorists and bringing them to justice. We are gathering information about where the terrorists may be hiding. We are trying to disrupt their plots and plans.

"Anything we do . . . to that end in this effort, any activity we conduct, is within the law," he said. "We do not torture."

Stressing that the obligation to protect Americans rests with both the executive and legislative branches, Bush said his administration is working with Congress as it battles terrorism.

"There's an enemy that lurks and plots and plans and wants to hurt America again," Bush added. "And so, you bet we'll aggressively pursue them, but we will do so under the law. And that's why you're seeing members of my administration go and brief the Congress. We want to work together in this matter."

He said, "I'm confident that when people see the facts, that they'll recognize that we've got more work to do, and that we must protect ourselves in a way that is lawful."

In Washington, Sen. Edward M. Kennedy (D-Mass.) charged that Bush's comments today and Cheney's effort to exempt the CIA from legislation against torture show that the White House has "learned nothing" from recent prison-abuse scandals.

"This administration has consistently sought legal justifications for harsh techniques, and their contradictory denials and stonewalling only make the war on terrorism harder to win and put our soldiers in further danger," Kennedy said in a statement.

En route back to Washington after visiting Brazil and attending a 34-nation summit meeting of Western Hemisphere leaders in Argentina, Bush was also asked about the prospects of congressional ratification of a U.S.-Panamanian free-trade accord, given declining support in Congress for regional trade pacts.

"The first step is to get the agreement done, and we're getting close," Bush said.

"I'll do my best to work in the Congress," he said, but "one area that we need to make progress on is with the Democrat Party." Injecting a rare partisan note on domestic politics into a foreign trip, Bush said that in previous congressional sessions, "the Democrat Party had free-trade members who were willing to make the right decisions, based not on politics but based on what's best for the interests of the country." However, "that spirit has dissipated in recent votes," he said, "and Panama can help reinvigorate the spirit. We can help to make sure this isn't just such a partisan issue."

Following the brief news conference, Bush and first lady Laura Bush visited the Corozal American Cemetery north of Panama City and were taken on a tour of the Panama Canal's Miraflores Locks by President Torrijos and his wife.

After returning to the United States on Air Force One, Bush is scheduled to address a rally for Jerry W. Kilgore, the Republican candidate for governor of Virginia, tonight in Richmond.