WASHINGTON — The Pentagon’s top uniformed lawyers took issue yesterday with a key part of a White House plan to prosecute suspected terrorism detainees, telling Congress that limiting the suspects’ access to evidence could violate treaty obligations.

Their testimony to a House committee marked the latest time that military lawyers have publicly challenged Bush administration proposals to keep some evidence — such as classified information — from accused terrorists. In the past, some military officials have expressed concerns that if America adopts such standards, captured American troops might be treated the same way.

The lawyers’ testimony contrasted with the panel chairman’s assertion that America must take a harder line when prosecuting suspected terrorists.

Rep. Duncan Hunter, a Republican of California who heads the House Armed Services Committee, said at the hearing that any military commission established to prosecute suspected terrorists must allow the government to protect intelligence sources. In saying so, Mr. Hunter aligned himself with the White House position.

“While we need to provide basic fairness in our prosecutions, we must preserve the ability of our war fighters to operate effectively on the battlefield,” Mr. Hunter said.

Mr. Hunter presented the military lawyers with various scenarios in which it might be necessary to withhold evidence from the accused if it would expose classified information. But the service’s top lawyers said other alternatives must be explored — or the case dropped.

“I believe the accused should see that evidence,” the Army’s Judge Advocate General, Major General Scott Black, said.

General Black and the other lawyers said such an allowance was a fundamental right in other court systems and would meet requirements under the Geneva Conventions.

But Mr. Hunter suggested that such a requirement could hamper prosecutions.

“Some of these acts of complicity in terrorist acts are very small pieces … and you don’t have a lot of evidence,” he said. The chairman repeated a scenario where the only piece of evidence would expose the identity of a secret agent and asked whether it would make sense to drop the case entirely.

“You get to the end of the trail, then yes, sir, you do,” General Black responded. The hearing came a day after Mr. Bush acknowledged for the first time that the CIA had secret prisons overseas and defended the practice of tough interrogations, and possibly torture, in attempt to force accused terrorists to disclose plots to attack America and its allies.

He said that 14 suspects, including the alleged mastermind of the September 11, 2001, attacks, had been turned over to the Defense Department and moved to the American detention center at Guantanamo Bay, Cuba, for trial.

Separately, State Department legal adviser John Bellinger III told foreign reporters yesterday that if additional suspected members of the Al Qaeda terror network were captured, “We reserve the right to have those people questioned by the CIA.”

Mr. Bellinger said foreign governments were free to decide whether to look for the locations of any CIA prisons on their territory, but “we are not going to talk about that.” European lawmakers yesterday demanded to know the exact location of the prisons.

The president proposed legislation Wednesday that he said would aid the government in prosecuting accused terrorists using secret military tribunals. The proposal left Republicans again divided over how the nation should treat potentially dangerous terror suspects, setting up a showdown in Congress just weeks away from elections when all members will try to sell themselves as tough on terror.

Those who said his policies were necessary to win the administration’s war on terror immediately praised Mr. Bush’s announcement.

Senator Frist, the majority leader and a Republican of Tennessee, said he would like to take up the bill on the Senate floor as soon as possible, leaving open the door for a vote on the measure before lawmakers break at the end of the month for election campaigning.

But some GOP moderates are challenging the proposal. They include three senators with hefty credentials: Senator McCain of Arizona, who spent more than five years as a prisoner of war in North Vietnam; a former military lawyer who still serves in the Air Force Reserves as a reserve judge, Senator Graham of South Carolina, and the chairman of the Armed Services Committee, Senator Warner of Virginia.

Senator Reid, the minority leader, said Mr. Bush’s decision to prosecute the suspected terrorists held by the CIA was long overdue. But, he added, the military commission system should be properly vetted through the Armed Services Committee.

“The last thing we need is a repeat of the arrogant, go-it-alone behavior that has jeopardized and delayed efforts to bring these terrorists to justice for five years,” Mr. Reid said.