Bush, on vacation at his ranch in Crawford, Texas, on Friday called Indian Prime Minister Manmohan Singh and "explained his decision to move forward on the sale", White House spokeswoman Dana Perino said.
Singh expressed "great disappointment", according to a spokesman in New Delhi, although US officials said Bush signalled a willingness to sell sophisticated fighters to India if it chose to buy them.
Pakistani Information Minister Shaikh Rashid Ahmad called Bush's decision "a good gesture... This shows that our relations are growing stronger."
A senior Bush administration official said the F-16 sale to Pakistan, which was blocked for 15 years, "will not change the overall balance of power" between Pakistan and India.
The official said the jets "are vital to Pakistan's security as President [Pervez] Musharraf takes numerous risks prosecuting the war on terror".
The US blocked F-16 sales to
Pakistan for 15 years
An administration official said the sale involved 24 planes, but another said the number could change. The F-16 is made by Lockheed Martin Corp, the largest US defence contractor.
Washington blocked the sale of the F-16s to Pakistan in 1990 as a sanction against its nuclear weapons programme.
Though no final decision has been made "at this point" on similar F-16 sales to India, a senior Bush administration official said: "We will respond positively to the Indian tender for bids to sell multi-role combat aircraft."
White House spokeswoman Perino said Bush and Singh discussed "India's request for information on the provision of multi-role combat aircraft for India" during their nine-minute conversation.
"The Indians are trying to decide which among a number of fighter aircraft to purchase. We are not the only potential supplier and we have announced that we will allow American companies to compete in that," a State Department official said.
The F-16 sale represents a major policy shift for the United States and a final step towards tacit acceptance of Pakistan's possession of nuclear weapons.
"The symbolism is important as it is a nuclear [warhead] delivery platform," said Uday Bhaskar, who heads the Institute for Defence Studies and Analyses, a government-funded New Delhi organisation.
Despite US assurances, New Delhi said the sale could affect the security balance.
"The prime minister expressed India's great disappointment at the decision, which could have negative consequences for India's security environment," Sanjaya Baru, spokesman for the prime minister's office, said.
"The prime minister expressed India's great disappointment at the decision, which could have negative consequences for India's security environment"
Sanjaya Baru, spokesman, Indian prime minister's office
Tensions between the neighbours, which have fought three wars and were on the brink of another in 2002, have eased since they began talks last year aimed at ending half a century of enmity.
India strongly opposed the sale of F-16s to Pakistan after the Pentagon cleared arms sales worth $1.2 billion to Pakistan last year. New Delhi says the planes could be used against it in a conflict.
Islamabad has said that any move by the United States to sell Patriot anti-missile systems to India will trigger a new arms race in the region, after a US defence team made a presentation last month in New Delhi.
"President Musharraf made a commitment to stand with the United States," the senior administration official said. "This is a long-standing request."