Iraq's prime minister made little headway in easing Iranian opposition to a US-Iraqi security pact, as Iran's supreme leader told him Monday that American troops must leave the country. The deal is already facing widespread rejection by Iraqi politicians, despite new proposals from American negotiators. Iran has staunchly opposed the agreement, which aims to set the framework for a longer-term US military presence in Iraq. Teheran feels the deal would solidify US influence in Iraq and give American forces a launching pad for military action against Iran. Iraqis, meanwhile, have so far rejected US drafts, saying they infringe on Iraq's sovereignty, giving American forces too much freedom to operate - and many fear Washington has plans to keep permanent bases, despite a denial of any such plan written into the draft. The latest proposed American draft, put forward Sunday, seeks to address some of those concerns. It adds an explicit promise that US forces in Iraq will not attack neighboring countries and that Iraqi authorities will be notified in advance of any action by US ground forces, two Iraqi lawmakers who saw the draft said. While it gives US forces the power to arrest suspects, it says any detainees would be handed over to Iraqi authorities, said the lawmakers, Mahmoud Othman and Iman al-Asadi. Hadi al-Amri, head of the Badr Organization, a pro-government Shi'ite party with close ties to Iran, said the latest draft was still unacceptable, and warned that the positions and interests of the two sides are so far apart that any kind of agreement is "impossible." US Embassy spokeswoman Mirembe Nantongo refused to comment on the specifics of the negotiations, which began in March. But, she said, "we have said publicly on numerous occasions that US forces in Iraq will not be used for offensive operations against any of Iraq's neighbors." The draft is the fourth put forward by the Americans, and earlier versions have been rejected by parties across Iraq's political spectrum, including Prime Minster Nouri al-Maliki's Dawa party, other Shi'ite parties in his coalition and Sunni Arab and Kurdish politicians. Al-Maliki has said he wants a deal that provides for a US troop presence on terms that respect Iraqi sovereignty. The prime minister has been meeting with Iranian leaders in Teheran the past three days, trying to ease Iran's opposition to the agreement - apparently hoping to stop Iranian denunciations and, in the long term, to ensure that an eventual agreement does not hurt ties with a country that is a close ally of his government. But in talks Monday, Iranian supreme leader Ayatollah Ali Khamenei made clear his rejection of any agreement. He said "occupiers who interfere in Iraq's affairs through their military and security might" are the main cause of Iraq's problems and the "main obstacle in the way of the Iraqi nation's progress and prosperity." He told al-Maliki that Iraqis must "think of a solution to free" the country from the US military," and he vowed that "America's dream for Iraq will not come true," according to state-run television. Al-Maliki returned to Iraq later Monday, ending his second trip to Teheran this year. US officials have accused Iran of trying to scuttle the negotiations. Teheran has considerable influence in Iraq: Besides its ties to mainstream Shi'ite and Kurdish parties, it is close to anti-US Shi'ite cleric Muqtada al-Sadr, whose followers have been holding weekly demonstrations against the security pact. The US also accuses Iran of funding and arming Shi'ite militiamen in Iraq, a claim Teheran denies. American officials believe Iran has used Iranian-backed terror groups elsewhere in the Middle East, notably Hizbullah in Lebanon, to stir up opposition to the security agreement across the region. Iranian officials and pro-government newspapers have accused Washington of trying to control Iraq through the security deal. Maziar Khosravi, an Iranian political analyst with the independent daily Mardomsalari, or Democracy, said Teheran was unlikely to accept any deal. "If the Iraq-US security deal is signed, America's influence will grow in Iraq and Iran's influence will decline," he said. If Baghdad signs an agreement, "Iran may reduce its cooperation with Iraq and avoid cooperation on security issues with the US and Iraq," he said. Iraq's parliament must approve the deal, and Iraqi officials familiar with the talks said Sunday that it stood no chance of passing without major changes in the US position. They said they believe a deal is unlikely to be reached before the end of President George W. Bush's term in January. The officials spoke on condition of anonymity because of the secrecy surrounding the negotiations. The Bush administration conceded for the first time that it may not finish the agreement before a new president takes office. A senior administration official close to the talks said it is "very possible" the US may have to extend an existing UN mandate. Iraqi and US negotiators are working on two agreements - one, a broad statement of principles on the countries' strategic relationship and the other a Status of Forces Agreement detailing the powers US forces will have in Iraq. The agreements would provide a legal basis for the presence of US forces after the current UN mandate expires at the end of the year. The target for completing the talks is July, but it seems likely that negotiations will last longer. The latest draft of the statement of principles includes a provision specifying that the US "does not seek to use Iraqi territory as a launching ground for offensive operations against other countries" and does not seek "to have permanent bases or a permanent military presence," according to an Arabic version of the draft obtained by The Associated Press. It also states that Iraq "temporarily gives the United States authority to carry out military operations in Iraq and the authority to detain individuals when security considerations require it."