The announcement was part of a new strategic approach to the troubled subcontinent that was presented to both countries by Secretary of State Condoleezza Rice on her visit there earlier this month.

"Existing military assistance will be supplemented by moving forward on the sale of F-16s to Pakistan and we're notifying that to Congress today," the official told reporters. He refused to say how many F-16s were involved.

But the official, who asked not to be named, added that "although the numbers involved are relatively small, there is no set limit on what the United States is going to be willing to sell to Pakistan."

The official said that the United States was also ready to boost defense cooperation with India, including the sale of F-16s, F-18s or other aircraft, to help it develop as a major power.

"The US will respond positively to the current Indian request for information on its bid for people who are willing to sell India its next generation of multi-role combat aircraft," the official said.

He said Washington was willing to work with New Delhi in other ways, including defense co-production and technology licensing, and covering areas such as command and control, early warning systems and missile defense.

But the planned sale of the F-16s to Pakistan, which reportedly wants to buy up to 25 of the aircraft, drew an immediate expression of anger from India, which has fought three wars with its subcontinent rival.

US President George W. Bush phoned Indian Prime Minister Manmohan Singh early yesterday to inform him of the plans and Singh expressed his "great disappointment at this decision," according to the Press Trust of India.

PTI quoted an Indian government spokesman as saying Singh conveyed his belief that the move could have "negative consequences for India's security environment."

India says that arming Pakistan with the sophisticated warplanes would upset the military balance in the region and cast a shadow over the slow dialogue process under way between the nuclear-armed neighbours.