Iran’s U.N. Ambassador Mohammad Khazaee didn’t attend the latest U.N. Security Council meeting on Iraq. But the moment the 3-hour session was over the Iranian delegation was circulating a strongly worded letter from Khazaee that had a very clear message for the administration of U.S. President Barack Obama: Stop talking like Bush.

He was responding to less than two dozen words on Iran in U.S. Ambassador Susan Rice’s speech to the council during a routine review of U.N. activities in Iraq. Rice said that U.S. policy “will seek an end to Iran’s ambition to acquire an illicit nuclear capacity and its support for terrorism.”

Those words clearly infuriated the Iranians, who have been toning down their anti-U.S. rhetoric since Obama took over from George W. Bush five weeks ago.

“It is unfortunate that, yet again, we are hearing the same tired, unwarranted and groundless allegations that used to be unjustifiably and futilely repeated by the previous administration,” Khazaee said in a letter to the council’s current president, Japanese Ambassador Yukio Takasu.

“Instead of raising allegations against others, the United States had better take concrete and meaningful steps in correcting its past wrong policies and practices vis-a-vis other nations, including the Islamic Republic of Iran.”

Khazaee’s remarks were among the most critical of the new U.S. administration by a senior Iranian official to date.

Is the Obama administration simply repeating the “same tired” language of the Bush administration? The accusations aren’t new, U.N. diplomats say, but the promises of a new approach could herald a radical shift in U.S. policy on Iran.

Obama, Rice and Secretary of State Hillary Clinton have said repeatedly that Washington would use all tools, including direct talks, to deal with Iran’s nuclear program, which Tehran says is for peaceful purposes.

Iran has reacted cautiously, saying it’s open to fair talks while demanding fundamental changes in U.S. policy. Western envoys in New York say that not everyone in the Islamic Republic is happy about the outstretched hand of Obama and his promises of change.

Tehran had often criticized the administration of former U.S. President George W. Bush, which labeled Iran a member of an “axis of evil” with North Korea and pre-war Iraq. It’s harder to criticize Obama at the moment, diplomats say. That could be one of the reasons Khazaee seized the opportunity to attack Rice’s speech to the council.

“The hardliners in Tehran find it easier to have a U.S. administration that turns its back on them,” said a European diplomat. “It’s easier to deal with a ‘Great Satan’. It gives them someone to blame their troubles on.”

It’s nearly three decades since Washington severed diplomatic relations with Iran in 1980 after militants stormed the U.S. embassy in Tehran and took a group of U.S. diplomats and officials hostage.

Present-day Iran, whose President Mahmoud Ahmadinejad has said that Israel should be “wiped off the map”, has repeatedly ruled out a suspension of the country’s uranium enrichment program, prompting the Security Council to impose three rounds of sanctions.

U.N. diplomats say that Obama administration officials have signaled that they do not believe the Iranian nuclear program can be stopped with U.S. or Israeli air strikes. Instead, Obama wants to use a combination of pressure – possibly by imposing further U.N. sanctions – and inducements to persuade the Iranians to halt their enrichment program. The details of the new approach are being worked out in a thorough review of the U.S. policy on Iran, U.S. officials say.

“Will a kindler, gentler U.S. approach work?” asked the European diplomat. “We’ll have to wait and see. Iran’s one of the countries that invented chess and it’s a very good player.”