A plea for clemency for the convicted spy Jonathan Pollard has been rejected by the Obama administration.

On Monday Israeli President Shimon Peres called on the White House to free the former

US Navy intelligence analyst, who was given a life sentence 15 years ago.

In his letter Mr Peres urged the US president to release the 57-year-old on humanitarian reasons. Pollard, who was found guilty of giving military secrets to Israel, was admitted to hospital last week.

Pollard's continued captivity remains a key issue for Israelis and for many Jewish Americans. He has always maintained that he only spied because the US authorities were withholding information crucial for Israel's security.

However the White House, continuing the stance of past Democratic and Republican administrations, said the spy's would not be released.

"Our position hasn't changed," said National Security Council spokesman Tommy Vietor.