Israel has refused to reassure President Barack Obama that it would warn him in advance of any pre-emptive strike on Iran's nuclear capabilities, raising fears that it may be planning a go-it-alone attack as early as next summer. The US leader was rebuffed last month when he demanded private guarantees that no strike would go ahead without White House notification, suggesting Israel no longer plans to seek Washington's permission", sources said. The disclosure [was] made by insiders briefed on a top-secret meeting between America's most senior defence chief and Benjamin Netanyahu, Israel's hawkish prime minister. Leon Panetta, the US defence secretary, flew into Israel last month on what was ostensibly a routine trip. Mr Panetta conveyed an urgent message from Barack Obama. The president, Mr Panetta said, wanted an unshakable guarantee that Israel would not carry out a unilateral military strike against Iran's nuclear installations without first seeking Washington's clearance. The two Israelis were notably evasive in their response, according to sources both in Israel and the United States. Alarmed by Mr Netanyahu's noncommittal response, Mr Obama reportedly ordered the US intelligence services to step up monitoring of Israel to glean clues of its intentions. What those intentions might be remains distinctly murky. Over the past fortnight, Israel's press has given every impression that the country is on a war footing, with numerous claims that Mr Netanyahu and Mr Barak are lobbying the cabinet to support the military option.