Washington: The White House stressed on Wednesday that Jonathan Pollard, an American jailed for spying for Israel, was guilty of "the most serious crimes" after a public Israeli request for clemency.
Israeli Prime Minister Benjamin Netanyahu made the unusually public appeal to President Barack Obama on Tuesday, and the White House said it was reviewing the issue.
But many observers feel it is unlikely that Obama would immediately grant the request, reasoning that the US intelligence community is opposed to such a step.
"I think it is important to underscore that Mr Pollard was convicted of some of the most serious crimes that anybody can be charged (with)," said White House spokesman Robert Gibbs.
Gibbs would not be drawn on the manner of the request, which saw Netanyahu, who has had a sometimes rocky relationship with the Obama administration, read out a letter to the US President in the Israeli parliament.
“Honourable President, in the name of the Israeli people I am turning to you to request a pardon for Jonathan Pollard," Netanyahu said.
Pollard, a former US Navy analyst, is serving a life sentence for passing thousands of secret documents about American spy activities in the Arab world to Israel between May 1984 and his arrest in November 1985.
The issue of Pollard, a US-born Jew who was given Israeli citizenship while in prison, has been a thorn in the side of relations between Israel and its main ally Washington.
His arrest sparked a crisis in ties that only ended with Israel promising to end all espionage activities on US soil.
But Israelis say Pollard`s punishment and the longstanding US refusal to commute his sentence have been particularly harsh, given that he gave information to a friendly nation.