WASHINGTON - A top aide to US President Barack Obama told Israel's leaders this weekend that there is still time for diplomacy to keep Tehran from getting a nuclear weapon, the White House said on Tuesday, amid growing concerns that Israel might resort to a preemptive strike.National security adviser Tom Donilon told Israeli officials that Washington shares their concern about Iran's nuclear push but also stressed the need to let sanctions work, White House spokesman Jay Carney said."We certainly understand the heightened concern that Israel has given its geographic location and other circumstances that are involved here for Israel," Carney told reporters, discussing Donilon's visit and the White House view on Iran's ambitions."Having said that, we believe that the approach this administration has taken has resulted in a level of consensus within the international community regarding Iranian behavior that has never been attained before that's resulted in a level of punitive sanctions that have never been attained before ... and that that has had an impact," he said. "We believe that there is time and space to attempt to resolve this peacefully."Iran says its nuclear program is meant to develop energy, not weapons.But its recent shift of uranium enrichment to a mountain bunker and refusal to negotiate guarantees that the program is peaceful have raised security fears - particularly in Israel - and also stoked concerns about Gulf oil supplies.Donilon was the latest in a series of high-level US officials who have traveled to Israel in recent weeks to impress US concerns over any attack on Iran.James Clapper, the US Director of National Intelligence, said last week he would soon visit Israel to discuss intelligence sharing.General Martin Dempsey, chairman of the US Joint Chiefs of Staff, who traveled to Israel last month, acknowledged in a weekend television interview that the two long-time allies have divergent views of the best course of action on Iran."I'm confident that (Israel's leaders) understand our concerns that a strike at this time would be destabilizing and wouldn't achieve their long-term objectives," Dempsey told CNN. "I also understand that Israel has national interests that are unique to them. And, of course, they consider Iran to be an existential threat in a way that we have not concluded that Iran is an existential threat."Speculation has been growing that Israel may attack Iran's nuclear facilities to set back the Islamic Republic's weapons progress. However, the head of the US Defense Intelligence Agency, Lieutenant General Ronald Burgess, told Congress last week that US intelligence agencies believe Israel has not made a decision to strike.It is widely believed that an outside attack on Iran would drive up oil prices, endangering the US economy and perhaps even Obama's chances for re-election. Obama, who has been criticized by Republican presidential candidates for being soft on Tehran, could come under pressure to back Israel in whatever action it took.Dempsey, the top US military officer, said in the CNN interview that a military strike on Iran would be premature because it is unclear Tehran will actually use the nuclear capabilities to build an atomic bomb.He said he was confident Israel knew that this was the US attitude, but stopped short of suggesting that the Americans had persuaded the Israelis that it was best not to attack Iran.On Tuesday, Carney repeated the White House took no options off the table in how to resolve the standoff but offered no details of what is being considered.Prime Minister Binyamin Netanyahu will meet Obama at the White House on March 5, and the day before the president will address an annual policy conference of the pro-Israel lobby group AIPAC, Carney said.