Senior officials in Israel are vehemently denying suggestions that it has been planning to blow up Pakistani nuclear sites. Israel has reportedly been developing precisely such plans for more than a decade.
Pakistan, which carried out a series of nuclear tests late last week, is understood to have been so terrified by the prospect of an eve-of-test Israeli attack on its nuclear programme that it appealed to both the United Nations and the United States government to intervene.
According to accounts of events last week now emerging in New York and Washington, Pakistan claims to have twice spotted what it assumed were Israel F-16 aircraft in its air space in the days before the tests were carried out. It feared that an Israeli raid, launched from India, was imminent.
Pakistan's ambassador to the UN, Mr Ahmed Kamal, is understood to have held a panic meeting with the Secretary-General, Mr Kofi Annan, on the subject; Pakistan also contacted US officials. American and UN officials, in turn, informed Israel of the Pakistani concerns, and both Israel's ambassador to the UN, Mr Dore Gold, and its ambassador to Washington, Mr Eliahu Ben-Elissar, got in touch with their Pakistani counterparts to convey messages of reassurance.
A spokesman for Israel's Prime Minister, Mr Benjamin Netanyahu, yesterday insisted that there was no basis to the allegations of a planned Israeli attack. A Defence Ministry spokesman issued a similar statement.
However, reports circulating in London as long ago as 1987 indicated that Israel - which enjoys strong defence ties with India, and is deeply concerned by the prospect of Pakistani nuclear know-how being transferred to Iran - has repeatedly proposed carrying out a joint strike against Pakistani nuclear installations.
In the mid-1980s alone, Israel reportedly tried on three separate occasions to interest India in a joint attack on Kahuta, the nuclear development plant in north-east Pakistan, just across the border from India.
On one occasion, in July 1985, Israeli officials held talks on the issue in Paris with a personal envoy of the then Indian Prime Minister, Mr Rajiv Gandhi.
Israel reportedly received detailed satellite photographs of the plant, and other top-secret US intelligence concerning operations there, via Jonathan Jay Pollard, a US defence analyst who is currently serving a life jail term in the US for spying for Israel.
Israel, said by foreign analysts to have a nuclear arsenal of some 100 warheads, has been unnerved by Pakistan's evident nuclear capability, and several politicians spoke yesterday of worries that nuclear technology could now be made available to Iran.
In the past, Israel has gone to extraordinary lengths to prevent potential enemies from achieving nuclear status. Most dramatically, in 1981, Israeli F-16s bombed Iraq's nuclear reactor at Osirak, destroying President Saddam Hussein's nuclear programme.
Iran's Foreign Minister, Mr Kamal Kharrazi, visited Islamabad in the wake of the tests, and praised Pakistan for creating "a balance in the region" to counter Israel. All Muslims, he said, now felt much more secure.
Mr Ehud Barak, the Israeli Labour Party leader who formerly served as his country's military chief of staff, yesterday described the Pakistani talk of an attack by Israeli F-16s as "a figment of their imagination" but confirmed that, technically, such an attack was feasible.
AFP adds from Washington: The US government has confirmed that it knew that Pakistan feared an Israeli attack on its nuclear sites but said it had concluded that such an attack was unlikely. "We have no information that it was ever a realistic danger," the State Department spokesman, Mr James Rubin, said.
Asked to comment on media reports about Islamabad's concerns, Mr Rubin said that while Washington was "aware of statements made by Pakistani officials" about the possibility of an attack, the US "had no information about this scenario".
Mr Rubin implicitly criticised Islamabad by saying that "to the extent that people cried wolf about a particular threat, their credibility has been damaged".
Tension between India and Pakistan had been intense since the Indian nuclear test on May 11th and 13th.