ISLAMABAD, PAKISTAN, OCT. 21 -- Accusations hurled in Pakistan's national election campaign have opened new fissures in this country's relationship with the United States, exacerbating doubts on both sides about the future of an alliance that was the centerpiece of U.S. policy in South Asia during the Cold War.

At nighttime stump meetings on dingy city streets and at huge countryside rallies, candidates associated with Pakistan's military-backed caretaker government have pounded away at the United States, accusing it of organizing partisan support for ousted prime minister Benazir Bhutto and even of fomenting a Zionist-Hindu conspiracy aimed at Pakistan's destruction.

While the high passions are expected to die down once the election is over, the rhetoric springs from serious differences between the United States and Pakistan, particularly on the issue of nuclear proliferation, that could lead to a break in the relationship, according to Pakistani and U.S. analysts.

The overriding question, these analysts say, is how to recast a four-decades-old alliance erected on Cold War foundations now that the Soviet threat in central Asia appears diminished, the war in Afghanistan is winding down, and emerging democracies in Eastern Europe are drawing a greater share of scarce U.S. foreign aid.

A strong constituency in the U.S. Congress appears ready to walk away from the close alliance with Pakistan -- which involves the largest disbursement of U.S. aid funds annually after Israel and Egypt -- if Islamabad's nuclear program is not reversed or if Wednesday's election is not seen as free and fair.

But Pakistani officials, apparently drawing support from the Pentagon and some sections of the State Department, argue that the United States cannot afford to alienate Islamic Pakistan at a moment when 200,000 U.S. troops are entangled in a precarious Persian Gulf confrontation.

"Your problems in the gulf are not going to disappear overnight and your problems with Iran are going to be there for a long time to come," said a retired senior military officer who was an architect of the U.S.-Pakistani alliance during the 1980s. "The United States needs reliable friends in the region."

Pakistan has dispatched about 5,000 troops to assist in the defense of Saudi Arabia against Iraqi aggression. But some U.S. analysts argue that given the new scope of U.S. military ties to the kingdom and its neighboring emirates, Pakistan's historical role as a potential springboard for defense of the gulf's oil supplies is less important than it once was.

For most of the years since World War II, the United States saw its alliance with Pakistan as a counterweight to Soviet ties with India and as a key segment of its strategy to curb Soviet expansion. Military and economic aid has not been continuous, however. Indo-Pakistani wars in 1965 and 1971 disrupted supplies, and the Carter administration cut aid during the late 1970s because of nuclear concerns. The Soviet invasion of Afghanistan in 1979, though, set the stage for unprecedented assistance levels during the 1980s.

This month's election campaign has become a lightning rod for Pakistani anger about the U.S. relationship. Senior members of the caretaker administration see Western pressure for a free and fair vote Wednesday as a smokescreen for pushing the relatively dovish Bhutto back into office. In their analysis, that would help the United States achieve a redefined set of policy goals in South Asia, such as controlling Pakistan's nuclear program and preventing war with India through reduction of covert military assistance for Moslem rebels in the disputed state of Kashmir.

In the caretaker government's view, effective lobbying in Washington by Bhutto following her dismissal as prime minister on Aug. 6 led to the Bush administration's decision to suspend $240 million in annual military aid because of nuclear-proliferation concerns, as well as to moves in Congress to make all aid to Pakistan contingent on the holding of a timely and impartial election.

Kamal Azfar, an adviser to interim Prime Minister Ghulam Mustafa Jatoi, charged that 53 U.S. senators -- who signed a letter earlier this month urging President Bush to withhold aid to Pakistan if a fair vote is not held -- "belong to a group opposed to the national interests of Pakistan."

U.S. officials respond that they have no favorites in the Pakistani vote and that they are pushing for free elections because they believe a stable democracy in Islamabad would be good for both Pakistanis and the West. They add that the suspension of U.S. military aid was required under U.S. law because Pakistan has taken concrete steps toward construction of an explodable nuclear device.

Pakistan's military leadership is said to argue that it needs a bomb to deter India, which tested a nuclear explosive in 1974 and refuses to submit to international inspection or to sign any nonproliferation treaties. Pakistanis also accuse Washington of applying a double standard when it presses for restrictions on the Pakistani program but continues to supply aid to Israel, which is widely believed to possess nuclear bombs.

Congressional and some other U.S. sources say they see little chance that any elected government in Pakistan will be able to provide the guarantees about Pakistan's nuclear program that U.S. law requires, since the program is closely managed by the military. But other U.S. officials hold out hope that satisfactory guarantees can be extracted after the election.

In this tense and complex standoff, each side feels it has leverage on the other. Besides their help in the gulf, Pakistani officials cite their military's contacts with Iran and China as a boon to the United States even in a post-Cold War era. And a U.S. analyst noted that Pakistan has extensive intelligence networks in Middle Eastern countries such as Syria, where U.S. intelligence reporting is said to be relatively weak.

The U.S. leverage derives mainly from the estimated $600 million in annual economic and military aid it provides Pakistan, as well as from several hundred million dollars more that has been directed to the Afghan resistance through the Pakistani military. The gulf crisis is seen as adding to U.S. economic leverage, since Pakistan is heavily dependent on imported oil and already is seeking Western financial assistance to help it through a foreign-exchange crisis caused by the recent spike in crude prices.