Teheran has accelerated its nuclear weapons program, including the production of atomic warheads, an exiled Iranian opposition group claimed in Belgium on Wednesday. "The Iran regime entered a new phase in its nuclear project," said Muhammad Mohaddessin, a representative of the Paris-based National Council of Resistance of Iran, while speaking at a news conference in Brussels. He said that Teheran had established a command and control center to work on a nuclear bomb for the first time, and that southeast of the capital a center was being set up to produce warheads. Iran has steadfastly denied it was working to obtain a nuclear bomb, arguing that its nuclear program was purely civilian. In December, the US National Intelligence Estimate said that Iran halted a nuclear weapons development program in 2003 because of international pressure. Mohaddessin said Iran had closed down one center only to open another later with the same purpose. He called the US report "not accurate." He said he had provided the latest information to the Vienna-based International Atomic Energy Agency on Tuesday and urged them to investigate more sites in Iran and to interview more scientists. "Lack of firmness by the international community has offered the regime the opportunity to get closer to obtaining the nuclear bomb," he contended. It was not possible to independently verify the NCRI claims, which Mohaddessin said came from sources within Iran, including some staff at covert nuclear plants. Four years ago, the group disclosed information about two hidden nuclear sites that helped uncover nearly two decades of secret Iranian atomic activity. But much of the information it has presented since then to back up claims that Iran has a secret weapons program has not been publicly verified. The NCRI is the political wing of the People's Mujahedeen of Iran, an opposition group that advocates the overthrow of government in Teheran. The Mujahedeen have been designated a terrorist group by Iran and by both the United States and the European Union. Teheran has insisted that such a group cannot provide correct information, leading the NCRI to call for a change in policy. "Maintaining the main opposition on the terrorist list is considered by the regime as an international license to acquire nuclear weapons," Mohaddessin said. In a statement, he also claimed that Iran's regime obtained aid from North Korea to help develop a warhead. To spread warnings about the dangers of Iranian nuclear capability, Israel was dispatching lawmakers to capitals in Europe and Asia, Foreign Ministry spokesman Arye Mekel said Wednesday. The Knesset members being sent, all of whom have diplomatic experience or military knowledge, are meant to make Israel's case that Iran is trying to become a nuclear power and urge more international sanctions to prevent that from happening, the ministry spokesman said. Around 15 lawmakers will head to Europe in the coming weeks as part of the project, Mekel said. "They will explain that Iran is continuing to produce nuclear weapons and that we must stop it, that the international community must mobilize because by 2009 Iran will know how to manufacture a nuclear weapon, or at least enrich uranium for that purpose," he said. The delegates are from parties across the political spectrum, including representatives from the coalition and from the opposition. "This shows that on this subject there are no political differences in Israel," Mekel explained. Israel has disputed the findings of the US intelligence report that Iran ceased pursuing nuclear weapons in 2003, and says that even if the Iranians are only enriching uranium for civilian purposes, the facilities could be transferred easily to manufacturing weapons. The first Israeli lawmaker to take part in the project, Yossi Beilin (Meretz), was already in Berlin on Wednesday meeting with German parliamentarians and other officials. "I'm here to explain the importance of the sanctions aimed at Iran," Beilin said in a telephone interview. "Even if the [US assessment] is accurate and the Iranians stopped their military program in 2003, they are still illegally enriching uranium, and that can be transferred to military use in a matter of months," Beilin said. "An Iranian nuclear weapon would mean the end of the political process" between Israel and its neighbors because it would bolster extremists and threaten moderates, Beilin said. Iran has already been slapped with two rounds of UN sanctions over its refusal to stop enrichment, and the US is pushing for further diplomatic pressure on Iran. Speaking on Wednesday, Iranian President Mahmoud Ahmadinejad said Iran had brought world powers "to their knees" by defying the sanctions. His statement was met by cheering supporters in southern Iran, ahead of a new report by the International Atomic Energy Agency on the country's disputed nuclear program. "They [US and its allies] expected the Iranian nation...to surrender after a resolution is issued or sanctions are imposed, but today...it has brought all big powers to their knees," Ahmadinejad told supporters in comments broadcast live on state television. The fiery leader vowed that Iran would not stop enriching uranium under any conditions. "The Iranian nation considers nuclear energy its definite right and does not accept any additional and cruel rules," Ahmadinejad said, alluding to a possible new round of United Nations sanctions. Addressing the US directly, Ahmadinejad warned that America and its allies would face a determined nation "if you start a new game." He did not elaborate, but was likely referring to Washington's efforts to push for a new round of UN sanctions.