Iraqi Prime Minister Nouri al-Maliki, right, is greeted by Iranian Defense Minister Mostafa Mohammad Najjar after al-Maliki arrived Saturday in Tehran, Iran.

Tehran, Iran ? Iraqi Prime Minister Nouri al-Maliki was in Tehran Saturday for talks that are expected to focus on a proposed U.S.-Iraq security agreement that Iran fears will keep the American military in neighboring Iraq for years.

The deal, which the Iraqis and Americans hope to finish by midsummer, would establish a long-term security relationship between Iraq and the United States. But critics say it will allow the U.S. to set up military bases across Iraq and allow it to use the country as a launching pad for military attacks in the region.

Washington and Baghdad are also negotiating a parallel agreement to provide a legal basis for keeping U.S. troops in Iraq after the U.N. mandate expires at the end of the year.

The talks on the security plan are secret, and neither Baghdad nor Tehran has confirmed it would be addressed in al-Maliki’s meetings. But ahead of the two-day visit, the prime minister’s party sought to calm worries by insisting that the deal would not allow foreign troops to use Iraq as a ground to invade another country – a clear reference to Iranian fears of a U.S. attack.

U.S. Congressional Democrats also have urged the Bush administration not to bypass Congress, which they believe should approve any deal. They fear a long-term security deal with Iraq – if it committed the U.S. to protecting Iraq – could make it difficult for the next president to withdraw U.S. forces from Iraq.

Hard-liners in Iran have warned that “the U.S.-cooked agreement turns Iraq into a full-fledged colony.”

Yet, the toughest words have come from Iraqi officials, especially those loyal to Muqtada al-Sadr, the anti-American cleric whose militiamen fought U.S. and Iraqi troops in Baghdad until a May truce ended seven weeks of fighting. Tens of thousands took to the streets in Baghdad’s Shiite slum of Sadr City on Friday to protest the agreement.

Its backers believe the deal would guarantee U.S. support as Iraq seeks to cement the security gains of the past year. It would also help assure Iraq’s Sunni Arab neighbors, notably Saudi Arabia, that Iraq’s Shiite-led government would not become an Iranian satellite.

U.S. officials have released no details about the negotiations, which began last March. But the U.S. alleges that Iran is encouraging a public campaign in Iraq against the proposed U.S.-Iraq security agreement, which the Iranians oppose.