President Mahmoud Ahmadinejad boldly declared Tuesday that US political influence in Iraq is "collapsing rapidly" and that Teheran is ready to help fill any power vacuum. The hardline Iranian leader also defended the neighboring country's embattled Shiite Prime Minister Nouri al-Maliki, who has recently faced harsh criticism by US politicians for his unsuccessful efforts to reconcile Iraq's divided Sunnis, Shiites and Kurds. "The political power of the occupiers is collapsing rapidly," Ahmadinejad said at a press conference, referring to US troops in Iraq. "Soon, we will see a huge power vacuum in the region. Of course, we are prepared to fill the gap, with the help of neighbors and regional friends like Saudi Arabia, and with the help of the Iraqi nation." Ahmadinejad did not elaborate how Iran would fill an eventual power gap in Iraq, but his remarks reflected what may be perceived as Iran's eagerness to have an increasing influence on its neighbor's political scene. His mentioning a Saudi role may have sought to allay regional fears that Ahmadinejad would want to dominate in Iraq. Even though Riyadh and Teheran have not cooperated in the past, it "doesn't mean it can't happen," Ahmadinejad said. State Department spokesman Tom Casey said Tuesday that the United States wants to see Iran play a more positive role in Iraq but that Ahmadinejad's remarks reflected "just more of the same Iranian rhetoric that claims to hold down support and friendship for the people of Iraq, while actions, unfortunately, take them in the opposite direction." In defending al-Maliki, Ahmadinejad accused the United States of interfering in Iraq's internal affairs and said any US effort to topple al-Maliki's government will fail. Key US Democrats including Sen. Hillary Clinton have called for al-Maliki to be replaced because his Shiite-dominated government has been unable to forge national unity. US President George W. Bush and the US ambassador in Iraq both have given blunt assessments of the political stagnation in Baghdad, and Bush has said it would be up to the Iraqi people to decide if their government deserved to be replaced. "They rudely say (the Iraqi) prime minister and the constitution must change," Ahmadinejad said of US critics. "Who are you? Who has given you the right" to ask for such a change, he added, addressing American critics of al-Maliki. For his part, al-Maliki has shrugged off the gloomy assessments, saying he would "pay no attention" to American critics and if necessary "find friends elsewhere." Ousting al-Maliki, a longtime Shiite political activist, would require a majority vote in the 275-member Iraqi parliament. And as long as the Kurdish parties and the main Shiite bloc stand beside al-Maliki, his opponents lack the votes for that. During al-Maliki's visit here earlier this month, Iranian leaders said that only a US pullout would bring peace to Iraq. "Occupation is the root of all problems in Iraq," Ahmadinejad said Tuesday. "It has become clear that occupiers are not able to resolve regional issues." Even as Ahmadinejad spoke, fighting between Shiite factions in southern Iraq raised new fears that a British troops pullout and waning US influence in the south could lead to chaos there that Iran may exploit. Ahmadinejad also called on the Bush administration to provide an answer as to why have 600,000 Iraqis been killed so far. "Who will answer for this? What was achieved?" Ahmadinejad dismissed the possibility of any US military action against Teheran, saying Washington has no plan and is not in a position to take such action. US has accused Teheran of being behind attacks on US troops in Iraq - a claim al-Maliki's government has only partially backed, saying Iran could have a role in the attacks. Iran has denied the charges. On another issue of contention, the US and its allies fear Teheran is using its civilian nuclear program as a cover to produce atomic weapons. Iran denies the charge, saying its program is solely geared toward generating electricity.