The White House on Tuesday rebuffed a call from Iranian President Mahmoud Ahmadinejad for face-to-face talks with his US counterpart Barack Obama, saying Iran was not serious about discussing its nuclear program.White House spokesman Robert Gibbs nonetheless held the door open to US-Iran talks as the State Department saw signs that Tehran may now be seeking a dialogue with Washington under the pain of new sanctions. "We have always said that we'd be willing to sit down and discuss Iran's illicit nuclear program, if Iran is serious about doing that," Gibbs told reporters. "To date, that seriousness has not been there." On Monday, the Iranian leader criticized Obama for missing "historic opportunities" to repair the broken relations with Iran and offered to meet him. "We are hopefully coming for the UN assembly," Ahmadinejad said in an address to expatriate Iranians which was broadcast live on state television. "We are ready to sit down with Mr. Obama face-to-face and put the global issues on the table, man-to-man, freely, and in front of the media and see whose solutions are better. We think this is a better approach."Ahmadinejad is expected to travel to New York for the UN General Assembly meeting next month.Washington and other nations say Iran's uranium enrichment program masks a drive for atomic weapons. Iran denies the charge, saying it is pursuing the peaceful use of nuclear energy. US State Department spokesman Philip Crowley said Iran may now be seeking a dialogue with Washington because it is feeling the bite of sanctions imposed by the UN Security Council, the United States, European Union and others. "The cost of doing business for Iran is going up," Crowley told reporters. "We're encouraged by what we're seeing... We sense that there may well be a willingness on the part of Iran to enter into the kind of dialogue that we have long sought," he added. He said that the series of sanctions are "getting Iran's attention." Crowley said he based his remarks on the result of Iran's contact with the European Union's top diplomat Catherine Ashton as well as on Iran's own public statements. Apart from Ahmadinejad's call for talks with Obama, Iran said on Friday it was ready for immediate talks with the United States, Russia and France over a confidence-building exchange of nuclear fuel. He added that it was also against stockpiling higher enriched uranium, as an apparent conciliatory move to the international community worried about its potential drive to obtain the grade of uranium needed for a nuclear bomb. Crowley said: "We are willing to meet Iran any time any place within the P5-plus-1." He was referring to the permanent five UN Security Council members - the United States, Russia, China, Britain and France - plus Germany, which have been leading the diplomatic efforts to curb Iran's nuclear ambitions