Iranian President Mahmoud Ahmadinejad is calling for a face-to-face debate with American counterpart Barack Obama at the United Nations. The offer came at news conference Monday as Ahmadinejad stepped up his campaign for reelection in the June 12 presidential vote. If returned to office, Ahmadinejad says he wants to meet Obama during the UN General Assembly in September to debate "world issues and the way toward peace." Ahmadinejad is in a four-way race against a fellow hard-liner and two pro-reform candidates. The campaign has grown more bitter in recent days with reformists accusing authorities of trying to undercut their strength by blocking the social networking site Facebook. Meanwhile, Iran has sent six warships to international waters, including the Gulf of Aden, to display its ability to confront any foreign threats, its naval commander was quoted by a local news agency as saying on Monday. Admiral Habibollah Sayyari was quoted by the Iranian Student News Agency (ISNA) as announcing the dispatch of the vessels only five days after Iran test-fired a surface-to-surface missile with a range of 2,000 km. The Islamic republic said that on May 14 it had sent two warships to the Gulf of Aden to protect oil tankers from the world's fifth-largest crude exporter against pirate attacks. It was not clear whether those two were of the six mentioned by the admiral on Monday. "Iran has dispatched six ... warships to international waters and the Gulf of Aden region in an historically unprecedented move by the Iranian Navy," Sayyari told a gathering of armed forces officials. He added that preserving Iran's territorial integrity in its southern waters called for the "perseverance and firmness" of the navy. The move to dispatch the warships was "indicative of the country's high military capability in confronting any foreign threat on the country's shores," Sayyari said. The ISNA report did not mention the threat of pirate attacks, which, fueled by large ransoms, have continued almost unabated despite the presence of an armada of foreign warships patrolling the Indian Ocean and Gulf of Aden. Also Monday, Ahmadinejad rejected the latest proposal by the West in its bid to bring Iran to halt its nuclear program. "The nuclear issue is a finished issue for us," Ahmadinejad told a news conference. "Our talks [with major powers] will only be in the framework of cooperation for managing global issues and nothing else. We have clearly announced this," Reuters reported. According to the proposal, made last year, Iran would freeze expansion of its nuclear program and in return the UN would freeze all economic sanctions against the country. Western diplomats say the offer still stands. "We will not allow anyone to negotiate with us outside the agency's regulations and issues," Ahmadinejad said, referring to the UN International Atomic Energy Agency. "Our activities will only be in the framework of the agency's regulations." The United States and its allies suspect Iran is seeking to build nuclear bombs, a charge Teheran denies. Obama offered a new beginning of diplomatic engagement with Iran if it "unclenches its fist." Asked about North Korea's nuclear test on Monday, Ahmadinejad said, "In principle, we oppose the production, expansion and the use of weapons of mass destruction."