Gates' brief stop in Israel was part of a parade of top Washington officials visiting Israel this week, with Iran and the expansion of Jewish settlements on Arab land the main topics. In each case, the Obama administration is taking a harder line with Israel than the positions taken by President George W. Bush.

Mitchell urged Israel to start "dealing with difficult issues like settlements." At the same time, he urged Arab nations to take "genuine steps" toward normalizing ties with Israel.

The differences over Iran come on top of US-Israeli disagreements over the Mideast peace process -- particularly Washington's calls for a halt to Israeli settlement building. The Obama administration is having to press Israel on multiple fronts at once, complicating its diplomacy as it makes a major push to revive Arab-Israeli negotiations.

All this comes at a time when Washington's policy of dialogue with Iran itself has hit an impasse because of that country's election turmoil.

Israeli Prime Minister Benjamin Netanyahu "reiterated the seriousness (with) which Israel views Iran's nuclear ambitions and the need to utilize all available means to prevent Iran from achieving a nuclear weapons capability," Netanyahu's office said following his meeting with Gates.

While the United States also reserves the right to use force if need be, the Obama administration is playing down that possibility while it tries to draw Iran into talks. Gates said Washington still hopes to have an initial answer in the fall about negotiations.

"The timetable the president laid out still seems to be viable and does not significantly raise the risks to anybody," Gates said in Israel.

Both Barak and Gates said time is short. Other officials have said Iran is perhaps one to three years away from being able to build a nuclear weapon.

Barak, speaking in both English and Hebrew, gave only lukewarm endorsement to the negotiating strategy.

"We are not in a situation in which we can tell the United States to hold, or not to hold discussions with Iran," Barak said. "But we repeatedly state our position in closed conversations, which is that a discussion like this should be limited in time, result-oriented, and able to decide if the Iranians are truly serious or not."

Itamar Rabinovich, a former Israeli ambassador to the US, said Israel "isn't anxious to launch military action."

"It doesn't want this, but Israel thinks more should be done and that diplomacy alone isn't enough. I think Israel and the US are on the same page but on different sides of the paper," he said.