The Iranian president emerged from meetings with his Iraqi counterpart Monday, saying the two countries have "one soul in two bodies."
Mahmoud Ahmadinejad said the United States, which has nearly 160,000 troops in Iraq in support of the government, wanted to block better ties between the Shiite Muslim-dominated nations.
"Iran completely supports freedom for the Iraqi people, the current political developments and national sovereignty. Those who have deployed hundreds of thousand military forces in Iraq are not interested in seeing better relations between our two countries," Iranian television quoted Ahmadinejad, as saying after meeting Iraqi President Jalah Talabani, who is paying a three-day visit.
Washington has accused Iran of meddling in Iraqi affairs after U.S.-led forces drove Saddam Hussein from power in April 2003. Iran denies the charge.
"History, religion, culture, geography and mutual interests have bound the two countries. Tehran and Baghdad have one soul in two bodies," Ahmadinejad said.
"A democratic, independent and developed Iraq will become Iran's best friend. Iran will stand by the Iraqi people," Ahmadinejad said.
Under Saddam, Iraq fought an eight-year war against Iran that killed more than 1 million people on both sides.
Talabani said he was looking for closer ties and help with terrorism.
"I have come to Tehran to deepen our strategic relations. I am sure that Iranian side will provide us with necessary help to uproot terrorism in Iraq," Talabani was quoted as saying.
Iran and Iraq formed five joint committees to deal with issues of political relations, reconstruction, the economy, trade and anti-terrorism during a July visit by Prime Minister Ibrahim al-Jaafari.
Talabani, who arrived from Cairo after attending an Iraqi reconciliation conference, was accompanied by ministers of electricity and planning and a deputy foreign minister.
Talabani also will meet Iran's supreme leader Ayatollah Ali Khameni.