NEW YORK - Clock ticks for Iran despite the US offer for talks, say diplomats, adding focus on improving relations is likely to have limits. As hopes grow for a moderate victory in Iranian election, many wonder how long Israel will wait before making a decision on whether to attack Iran’s nuclear site

The United States will push for new U.N. sanctions against Iran later this year if President Barack Obama's effort to improve relations fails to stop Tehran from pursuing its nuclear program. But plans for a fourth round of international sanctions will remain on hold at least until after Iran's presidential elections in June, diplomats said.

There are hopes in Washington and other Western capitals that a moderate will win the Iranian election and seize upon President Barack Obama's recent offer of new diplomatic engagement with the Islamic Republic. Iran's nuclear policy is controlled by its supreme leader, Ayatollah Ali Khamenei, not the president. But a victory for conservatives - Iranian officials reacted coolly to Obama's videotaped offer and vowed to continue their uranium enrichment program - could lower the chances of success of Obama's new strategy.

The U.S. and Western allies suspect Iran is secretly developing nuclear weapons, as does Israel. But Tehran insists its program is geared to generating electricity and boosting its oil exports. More important than the outcome of the Iranian vote, analysts said, is the question of how long Israel will be willing to wait to see if the U.S. approach is working before taking a decision on whether to attack Iran's nuclear sites.

Mark Fitzpatrick, a former U.S. State Department official and nonproliferation expert at the International Institute for Strategic Studies, said Iran will not have much time after its elections to change gears on the nuclear front. "Israel is not going to wait forever," he said. "I couldn't give you a prediction of months, but I don't think that Iran has all that much time. They have an opportunity now and they should seize it."

Months, not years

Israel's new leader appeared to confirm that assessment in an interview with a U.S. magazine. Israeli PMBenjamin Netanyahu and several of his military aides told Atlantic magazine this week that Israel would not wait too long. One Israeli military aide was quoted as saying Israel's time lines are now drawn in months, "not years."

Israel bombed Iraq's nuclear reactor at Osiraq in 1981 and has suggested it was prepared to do the same in Iran. Obama's shift from his predecessor's policy of isolating Tehran has backing from UK, France and Germany. These countries are helping to spearhead efforts to persuade Iran to freeze its enrichment program in compliance with U.N. resolutions. Russia and China have also welcomed the overture.

At the same time analysts and diplomats said Obama would be realistic about its chances of a breakthrough on the Iranian problem and was aware that Iran may use talks to buy time to complete its nuclear program. Work on a new sanctions resolution would likely commence later this year if Iran continues enriching uranium, the diplomats said, but the focus at the moment will be on engagement, not punishment.

"He's (Obama) not going to be comfortable right off the box threatening," said Henry Sokolski, head of the Nonproliferation Policy Education Center. "They've branded themselves as the engagers and they'll stick to the brand for now."

Iran's progress in developing it's nuclear capability is also likely to provide a limit to Western patience. The U.N. nuclear watchdog reports that Iran is making progress in purifying uranium using difficult centrifuge technology. According to one Western diplomat, that trend is "unsettling" and "cannot continue indefinitely."