WASHINGTON: US President Barack Obama's new diplomacy is hitting higher hurdles than expected, with Iran's disputed vote, Israel's refusal to halt settlements and North Korea's persistent provocation.

In his first public comments since the disputed re-election of President Mahmoud Ahmadinejad, Obama said Monday that he was "deeply troubled" by post-election violence in Iran, as police cracked down on protestors in one of the worst crises since the Islamic revolution of 1979.

But the US president, who called on Iranian leaders to respect free speech and democracy after the reported death of an opposition protestor in Iran, said "it is up to Iranians to make a decision about who Iran's leaders will be." The Obama administration stopped short of echoing European Union calls for a probe of results that gave incumbent populist leader Ahmadinejad 63 percent of the vote.

State Department spokesman Ian Kelly said he had not seen the EU requests, but added: "I would say that Iran needs to take seriously these ... allegations and needs to examine these accusations very thoroughly." As the new administration wants to keep its hand "outstretched" to Tehran, which Obama's predecessor George W. Bush sought to isolate, Kelly also stopped short of denouncing the Iranian crackdown on protesters.

"We're concerned about some of the treatment of demonstrators, and we're calling for ... the Iranian authorities to respect the right of people to express themselves peacefully," he said.

Karim Sadjadpour, an analyst with the Carnegie Endowment for International Peace, said: "America and Europe are totally different forces in Iranian domestic politics. "By prematurely inserting ourselves into the Iranian political debate we may unwittingly hurt those whom we're trying to help," Sadjadpour told AFP.

"The administration should certainly not acknowledge the results of these fraudulent elections, but we should refrain from denouncing them. They should continue to say they're watching with interest and concern." Such a position seemed all the more important as Terror Free Tomorrow, a non-government organisation that studies public opinion, said that Ahmadinejad may well have won the election.

The group, which conducted a telephone survey of 1,001 Iranians between May 11-20 in the country's 30 provinces, said Ahmadinejad had more than twice as many people who intended to vote for him than for his rivals. Another hurdle to Obama's bid for a fresh start in the Middle East is the refusal by the right-leaning government of Israeli Prime Minister Benjamin Netanyahu to freeze settlements -- a stumbling block to Palestinian statehood.

Ten days after Obama's speech in Cairo aimed at reconciling with Arabs and Muslims, Netanyahu on Sunday rejected three key points: a freeze in settlements, a withdrawal from the occupied Arab part of Jerusalem and a return of Palestinians to homes they fled when Israel was created in 1948.

And the Israeli leader placed conditions for a future Palestinian state, such as denying it an army and requiring it to recognise Israel as a Jewish state. Still, the White House played up the positive, calling it "an important step" forward, as Netanyahu recognised for the first time the principle of a Palestinian state, although it did not deny that the Israeli premier's demands posed difficulties for the administration.

The US response was also muted toward new developments from North Korea, yet another thorn in Obama's side.

A defiant Pyongyang vowed Saturday to build more nuclear bombs and start enriching uranium for a new atomic weapons programme after the UN Security Council imposed sanctions for its May 25 nuclear test.

"I don't want to get into a situation where we're responding to every ... every bellicose and dire action and statement coming out of North Korea," Kelly said.

But Obama may shed light on his plans to deal with the thorny North Korea issue Tuesday, when he meets with South Korean President Lee Myung-Bak, who is seeking security guarantees from the United States as a standoff escalates with the nuclear-armed North.