President Clinton has removed Syria and Lebanon from the list of countries that play an important role in producing or shipping illegal drugs, overcoming objections from officials within the administration who argued that progress in the two countries was insufficient to merit the change.

Senior administration officials said the decision, made public yesterday in a letter from Clinton to Sen. Charles E. Grassley (R-Iowa), was a recognition of the two countries' successful eradication of the cultivation of poppy plants in Lebanon's Bekaa Valley, previously an important source of heroin for Europe and the United States.

Grassley, chairman of the Senate Caucus on International Narcotics Control, sharply disagreed with the decision, saying removing Syria from the list was "simply a blunder."

Last week, Grassley blocked a Senate vote on four nominees to ambassadorial posts in Latin America to show his displeasure with the failure of the White House to meet a Nov. 1 deadline for submitting the list. Once he received a copy of the letter, an aide said, Grassley released his hold on the nominees, who were confirmed yesterday.

Administration officials defended the decision, saying that both countries had made progress in improving their anti-narcotics records. The officials said the decision was independent of the Middle East peace process, in which administration officials have long sought the cooperation of Syria.

"This was not a political decision, it was made on the facts," one official said. "The countries did not meet the legal definition of major drug-producing or drug transit countries."

The decision is a sharp reversal from last year, when Syria was among six countries "decertified" by the United States for its failure to stem the flow of illegal drugs. The decision to remove Syria and Lebanon from the list of 30 countries that are major drug producers or transshipment points means that they will not be considered for decertification when the annual process is taken up next spring.

Although Syria no longer would be subject to sanctions that are applied to decertified countries, it would continue to be the object of U.S. sanctions because U.S. officials regard it as a supporter of terrorism.

Administration officials said the list was delayed because of debate within the administration over Lebanon and Syria, which were the only countries removed this year from last year's list.

In his letter, Clinton said the joint Syrian-Lebanese effort to eradicate Bekaa Valley opium poppy cultivation had been "effective, since U.S. government surveys have detected no current opium poppy cultivation."

Both countries remain "transit areas for South American cocaine, and small laboratories in Lebanon reportedly refine Southwest Asian opium into heroin destined for Europe and the West," Clinton wrote, but "there is no evidence that any of these drugs reach the United States in quantities that significantly affect the United States."