Washington ? Vice President Dick Cheney and CIA director George Tenet on Thursday gave congressional leaders a top-secret briefing on the threat from Iraq as President Bush came under mounting pressure to win international approval for any military action.

Senate Republican Leader Trent Lott of Mississippi said the classified briefing included some “interesting and troubling information” that will give members of Congress “a lot more to think about” in deciding how to deal with Iraq. He declined to elaborate.

Senate Majority Leader Tom Daschle of South Dakota was equally tight-lipped but his tone changed after the closed-door meeting in the Capitol. Daschle, a war skeptic who had earlier complained that the Bush administration had failed to answer key questions, called the session “very helpful.”

But the briefing was unlikely to alter Daschle’s view that Bush should seek the United Nations’ support for any military operation. Following Bush’s promise to seek a vote of approval on Capitol Hill for any action against Iraq, the focus shifted Thursday to the U.N.’s role.

Lawmakers in both parties joined a host of world leaders in urging Bush to follow his father’s lead before the Persian Gulf War by enlisting the U.N. in his cause. A 1990 U.N. resolution authorized the United States and its allies to use “all necessary means” to force Iraq out of Kuwait.

“I would hope that he could get the kind of support from the U.N. that his father did,” Daschle said. “It would certainly be in the president’s best interest, our country’s best interest, for him to go to the Security Council, to the United Nations, to solicit their support.”

Daschle added, “If he does that and fails it makes it harder for us as a country” to launch an attack.

A senior administration official said Bush had not decided whether to seek a U.N. resolution supporting military action. But the official, who insisted on anonymity, said administration officials are convinced that they need to rally international support, rather than go it alone.

Rep. Henry Hyde of Illinois, a leading Republican, urged Bush to work with the United Nations for another round of weapons inspections in Iraq. Hyde predicted that Iraq would rebuff unfettered inspections, which would strengthen Bush’s case for military action.

Russia, France and U.S. allies in the Arab world have been among the most insistent on the need for U.N. involvement. German Chancellor Gerhard Schroeder said Germany’s constitution would prohibit his country’s cooperation in any military campaign that did not have U.N. backing.

Danish Prime Minister Anders Fogh Rasmussen, whose country holds the presidency of the 15-nation European Union, also has called for U.N. approval for any military campaign.

Bush will look for ways to win over world opinion today in a series of phone calls to the leaders of China, Russia and France. Those three countries, along with the United States and the United Kingdom, have veto power on the 15-nation U.N. Security Council.

The president will meet Saturday with British Prime Minister Tony Blair at Camp David, the presidential retreat in Maryland.

Bush plans to present his case on Iraq to the U.N. general assembly in New York on Thursday, a day after attending a Sept. 11 memorial service.

“I will remind them that history has called us into action, that we love freedom, that we’ll be deliberate, patient, strong in the values that we adhere to,” Bush said Thursday in a preview of today’s phone calls for an audience in Louisville, Ky.

“We can’t let the world’s worst leaders blackmail, threaten, hold freedom-loving nations hostage with the world’s worst weapons.”