Benjamin Netanyahu has announced that he will push President Barack Obama for the release of a Jewish American jailed by the US for spying in 1987.
The Israeli prime minister said in a statement that he would press for the release of Jonathan Pollard "in a formal and public manner".
However White House officials dismissed the possibility of letting the former Navy intelligence analyst out of prison early.
President Obama’s press secretary, Robert Gibbs, said: "I am not aware that that's something that the president is looking at doing.”
Mr Pollard was charged with giving military secrets to Israel and given a life sentence, despite claiming that he spied because the US was withholding information crucial for Israel’s security.
The 56-year-old is not due to be released from the North Carolina prison he is serving in for another five years, but his continued imprisonment is a key cause for Israel’s right-wing and for Mr Netanyahu.
Mr Netanyahu granted Mr Pollard Israeli citizenship in 1995 when he was first prime minister. He said he had raised the issue with President Obama and Secretary of State Hillary Clinton on several occasions.
Speaking on Israeli radio, he said: "I worked very hard in my first term as prime minister to get Jonathan out.
"I intend to succeed in my second term. I think we can do it."
In September there was speculation in the Israeli media that Mr Netanyahu’s office had discussed with American negotiators the possibility of Israel making concessions, including on settlement building, in return for Mr Pollard’s release.