Former presidential candidate John McCain has added his voice to a growing number of high-profile US politicians demanding the release of convicted spy Jonathan Pollard.

According to Israeli Prime Minister Benjamin Netanyahu, Senator McCain offered his support for the cause during a telephone conversation yesterday.

Earlier this week Henry Kissinger, secretary of state during the Nixon administration, backed the campaign to secure Mr Pollard’s freedom five years before his sentence expires.

A Navy intelligence analyst, Mr Pollard was charged with giving military secrets to Israel and given a life sentence in 1987.

He maintained that he spied because the US authorities were withholding information crucial for Israel’s security.

His continued incarceration is a source of contention for right-wing groups in both Israel and the US. Last year Mr Netanyahu announced he would push President Barack Obama for Mr Pollard’s relaese, but the White House refused to contemplate doing so.

Other figures who have called for Mr Pollard’s sentence to be cut include the ex CIA director James Woolsey and former Pennsylvania senator Arlen Specter.