VISITING foreign leaders like King Hussein of Jordan or Prime Minister Benazir Bhutto of Pakistan are likely these days to spend almost as much time prowling the halls of Congress as being wined and dined by the president. That is because Congress, playing an increasingly aggressive role in foreign policy, can no longer be counted upon to deliver what the president has promised.
At issue here is not just the tendency of the Republican leadership to exercise control over future commitments, such as support for United Nations peacekeeping. More disconcerting to the administration is the willingness of Republican leaders to upset initiatives already undertaken, most often in consultation with Congress -- albeit a past, Democratic-controlled Congress.
''America must prove as good as its word -- our credibility is at stake,'' a frustrated Vice President Al Gore said in a speech to the Washington Institute for Near East Policy.
He was speaking shortly after the $275 million in debt forgiveness that President Clinton had promised to King Hussein as part of the Israeli-Jordan peace package had become enmeshed in an anti-foreign aid rebellion in Congress. It was finally attached by Sen. Bob Dole (R) of Kansas to a $16 billion spending-cut bill as insurance against a veto.
''The days of checkbook diplomacy are over,'' said Sen. Mitch McConnell (R) of Kentucky, chairman of the Senate foreign operations subcommittee. An embittered King Hussein was quoted by columnists Evans and Novak as saying, ''I am not a beggar or a rug merchant.'' Other long-standing commitments are in jeopardy. Aid to Egypt is threatened with a drastic cut. The $500 million promised to the Palestine Liberation Organization as a sweetener to achieve a peace agreement with Israel is being held hostage by Congress to the PLO's performance in combating terrorism.
The bizarre problem that arose with Pakistan had an earlier origin. In 1990 an amendment authored by Sen. Larry Pressler (R) of South Dakota, intended to discourage Pakistan from nuclear weapons development, was invoked to halt delivery of $1.4 billion in fighter bombers and other equipment already paid for. Since then Pakistan has not been able to get either the planes or the return of its money. A clearly embarrassed Mr. Clinton, appearing with Mrs. Bhutto at the White House, promised to consult Congress, saying, ''I don't think it's right for us to keep the money and the equipment.''
Senate Finance Committee chairman Alfonse D'Amato (R) of New York moved for cancellation of the Mexican loan guarantee, then relented for the time being, adding to Mexico's sense of insecurity.
As embarrassing as any cutback forced on the administration was the announcement that the American delegation had to make to the 22-nation Food Aid Convention last month. The American share in the international commitment of food for hungry countries had stood at 4.7 million metric tons for 20 years. Now it was reduced almost by half, to 2.8 million.
The European Union criticized the United States for going back on obligations of food desperately needed in Africa and former Yugoslavia. The American delegation said it had no alternative in the face of Republican pressure to reduce foreign aid.
If other nations must reckon with America reneging on its pledges because the complexion of Congress has changed, then peacekeeping becomes difficult and American leadership becomes questionable. ''Deadbeat dads'' is a name for fathers who don't honor commitments to their children. Perhaps ''Deadbeat Uncle Sam'' will become the name for a superpower that doesn't honor its commitments to the world.