YASOUJ, Iran — Iranian President Mahmoud Ahmadinejad said Wednesday that the United States' participation in the latest round of nuclear talks is a step toward recognizing Tehran's right to acquire nuclear technology.

A senior diplomat from the U.S. joined envoys from five other world powers in Switzerland at Saturday's talks on Iran's nuclear program. Ahmadinejad told thousands of supporters gathered in the southern Iranian town of Yasouj that U.S. Undersecretary of State William Burns "spoke politely and in a dignified manner."

"It was a step toward recognizing the rights of the Iranian nation, toward justice, toward repairing your image in the world, toward cleaning 50 years of crimes you committed against the Iranian nation," Ahmadinejad said, addressing the U.S.

The United States and other Western nations accuse Iran of seeking to acquire nuclear weapons and demand that it freeze its uranium enrichment program. Iran says its nuclear program is for peaceful purposes. Ahmadinejad on Wednesday again vowed Iran will not "retreat one iota" from pursuing it.

The U.S. participation in the Geneva talks had raised expectations for a compromise under which Iran would agree to stop expanding its enrichment activities. In exchange, six world powers — the U.S., Germany, Britain, France, Russia and China — would hold off on adopting new U.N. sanctions against Iran.

German Chancellor Angela Merkel said negotiators were hearing "very diverse signals" from Iran on its intentions but that she still expects a diplomatic solution. "I am counting on that and nothing else," she told reporters Wednesday.

In France, which currently heads the European Union, Foreign Minister Bernard Kouchner said he wasn't surprised that Ahmadinejad "declared he won't budge" because the Iranian president has proved "quasi-unable to show political flexibility."

"It's always disappointing to see how peace efforts are opposed by a tenacity ... that doesn't benefit the Iranian people," Kouchner said.

He said the slow beginning to the Geneva talks did not mean a diplomatic solution would not be found. "The Iranian (negotiators) we are sent are much more flexible than President Ahmadinejad," he told reporters.

U.S. Secretary of State Condoleezza Rice on Monday accused Iran of not being serious at the Geneva talks. She said Iran had given the run-around to the envoys, while all six nations were serious about a two-week deadline for Iran to agree to freeze suspect activities and start negotiations or else be hit with new penalties.

Iran already has defied three sets of U.N. sanctions over its uranium enrichment activity.

But recent Iranian pronouncements suggest the Islamic Republic may be looking to improve ties with the United States, with officials speaking positively about the possibility of opening an interests section in Tehran after closing its embassy there decades ago.

Ahmadinejad urged the United States to continue its "positive" attendance in the talks.

"I advise you not to ruin the positive step you took through irrelevant words and claims," he said.