Secretary of State Madeleine K. Albright yesterday gave her strongest endorsement yet to political opponents of Yugoslav President Slobodan Milosevic, pledging to lift economic sanctions against Yugoslavia in exchange for clean elections that U.S. officials say would inevitably force Milosevic from power.

Flanked by leading members of the Serbian opposition, Albright said at a State Department news conference that the United States would work with its European allies to promote the reform of media and election laws in Yugoslavia. And she gave qualified support to a European Union program to provide emergency heating oil to two opposition-controlled Serbian cities.

"In talking to these democratic leaders, I was able to visualize with far greater clarity the potential of a new reality for Serbia," Albright said. "There is no question that the thirst for change, freedom and accountability and for an end to corruption, arrogance and repression is deeply felt."

Albright's pledge to support the lifting of economic sanctions in exchange for free and fair elections appears to mark a shift in administration policy, which previously called for sanctions to be lifted only after Milosevic has been removed from power.

In practice, however, there may be little difference: According to a survey of Serbian public opinion by the American polling firm of Penn, Schoen & Berland Associates, the Yugoslav leader is hugely unpopular at home and would be soundly beaten, 47 percent to 18 percent, in a fair contest with the Alliance for Change, a coalition of Serbia's main democratic political parties and groups. The poll was conducted on behalf of the Washington-based National Democratic Institute.

"I find it really, really, really hard to believe that Milosevic might win a free and fair election," Albright said after meeting with leaders of the alliance, including Dragoslav Avramovic, an economist and former governor of the Yugoslav central bank; Zoran Djindjic, president of Serbia's Democratic Party; and two leading opposition mayors, Zoran Zivkovic of Nis and Vladimir Illic of Cacak.

"The reality is there's not going to be any lifting of sanctions so long as Milosevic is in power," said James R. Hooper, a former diplomat who now directs the nonprofit Balkan Action Council. "But the whole point is, if you have free and fair elections, that is going to solve that conundrum."

After conferring with Albright this morning, the opposition leaders met with White House national security adviser Samuel R. "Sandy" Berger. The high-level reception dramatizes the administration's newfound commitment to the opposition, which has long been perceived in Washington as weak and divided. The leaders came here under the auspices of the nonprofit group Freedom House.

"I think the visit is a real breakthrough," Hooper said. "It gave the administration a chance to project that the Alliance for Change is the vehicle for change within Serbia."

As a sign of that commitment, Albright reiterated that the United States will "evaluate" a European Union program to supply heating oil to two Serbian cities controlled by the opposition with an eye toward possibly supporting its expansion to other municipalities. Administration officials have been torn between their desire to avoid blame for humanitarian suffering in Serbia and concern that the oil could help bolster Milosevic's regime.

Zoran Zivkovic, the mayor of Nis, said that denying the oil would be a mistake. "That can help only those forces that want to achieve the total isolation of Serbia," he said in a meeting with Washington Post reporters and editors on Tuesday. "It would prove their theory that the entire world is united against Serbia."