The letter was given to the AP a day after UPA government won a confidence vote that paved the way for a landmark deal on nuclear energy cooperation with the United States. To finalize the US deal, India must strike separate agreements with the International Atomic Energy Agency as well as the Nuclear Suppliers Group of countries that export nuclear material. Then Congress will need to approve the accord.

The agreements would end more than three decades of nuclear isolation for India, opening its civilian reactors to international inspections in exchange for the nuclear fuel and technology it has been denied because of its refusal to sign the Nuclear Nonproliferation Treaty and its testing of atomic weapons.

India imports about 75 per cent of its oil, and the Prime Minister has argued the country needs the nuclear deal to power its financial growth and lift hundreds of millions out of poverty.

The 35-nation IAEA board is expected to approve on Aug 1 a safeguards agreement setting up rules for inspecting some of India's civilian nuclear facilities. Approval of the safeguards deal is key in India's efforts to gain access to legal imports of nuclear fuel and technology from the 45-nation Nuclear Suppliers Group.

Pakistan's letter dated July 18 addressed more than 60 nations including members of the IAEA board and Nuclear Suppliers Group. It warned the safeguards agreement would hurt nonproliferation efforts and "threatens to increase the chances of a nuclear arms race in the subcontinent."

Predominantly Hindu India and Muslim Pakistan have fought three wars since they were created in the bloody partition of the Indian subcontinent at independence from Britain in 1947.

Relations have improved considerably since the start of a peace process in 2004. But progress at the talks has been slow and deep distrust remains between the two rivals, which developed their nuclear arms in secret.

The Nuclear Suppliers Group bans exports to nuclear weapons states such as India and Pakistan that have not signed the Nuclear Nonproliferation Treaty and do not have full safeguard agreements allowing the U.N. nuclear watchdog to inspect their facilities. But the Nuclear Suppliers Group is ready to consider a waiver for India, in part due to lobbying from Washington.

The Bush administration has signed a deal to supply India with nuclear fuel but needs approval, first from the Nuclear Suppliers Group and then Congress.

In India, US Ambassador David Mulford said earlier Wednesday Washington hoped New Delhi would quickly finalize the deal so it could be presented to Congress for approval in early September.

"We are delighted that this has taken place and we are organizing ourselves and stand ready to move ahead with the final steps of the civil nuclear initiative," Mulford told reporters.

Pakistan is vehemently opposed to the Nuclear Suppliers Group doing business with its rival and may vote against approval of the draft at the Aug. 1 IAEA board meeting.

The IAEA board is expected to approve the deal despite criticism from detractors that it could limit international oversight of New Delhi's civilian facilities because of ambiguous wording and help supply its arms program with fissile material.

Indian Prime Minister Manmohan Singh was forced to call a confidence vote Tuesday after communist political parties withdrew their support for his government this month to protest the agreement, fearing it would draw India closer to the US.