NEW DELHI, FEB. 16 -- India's Congress Party announced today that it would help topple Prime Minister Chandra Shekhar unless his government withdraws refueling rights granted to U.S. transport planes ferrying supplies to the Persian Gulf.

The threat follows weeks of argument among politicians over India's decision to permit U.S. C-130 and other transport planes to refuel at three Indian airports en route from the Philippines to the gulf war theater.

The Congress Party's warning carries considerable weight since Shekhar, a Socialist who took office last November, depends on its support to retain power. Led by former prime minister Rajiv Gandhi, the Congress Party holds the largest number of seats in Parliament.

Ghulam Nabi Azad, the party's general secretary, told a news conference today that the Congress Party would not oppose a no-confidence motion against Shekhar's government unless the refueling is halted. Leftist parties are expected to offer such a motion over the issue when Parliament reconvenes Feb. 21.

A decision to deny landing rights to U.S. transport planes would likely have a minimal impact on U.S. logistics in the gulf.

Criticism of Shekhar has increased during the last two weeks because of concerns about civilian casualties in Iraq and the U.S. bombing campaign.

Azad declined to elaborate on the reasons for his party's decision, but it coincides with a widespread perception here that the United States and its allies rejected Iraq's conditional offer to withdraw from Kuwait, announced Friday, too quickly and too harshly.

A U.S. Embassy spokesman declined comment on the Congress Party's announcement.

In granting refueling rights to the United States, Shekhar modestly redirected India's decades-old foreign policy, which has been marked by strong support for the Nonaligned Movement, close ties to the Soviet Union and harsh anti-Western rhetoric. The United States responded by helping to facilitate loans to India from the International Monetary Fund.

Shekhar has defended his move by expressing support for the U.N. resolutions adopted after Iraq's invasion of Kuwait and by saying the United States has assured him that the transport planes refueling daily at Bombay, Madras and Agra carry only non-lethal supplies.

Other Indian leaders backed the prime minister's decision because they saw support for the U.S.-led coalition as a way to wean the United States from its traditional ally in South Asia, Pakistan, India's longtime enemy. U.S.-Pakistani relations are at a low point.