Ahmadinejad's visit to Baghdad, the first by an Iranian leader since the devastating 1980s war between Iran and Iraq, saw him meet with his Iraqi counterpart, Jalal Talabani.
"Our countries have the same viewpoint on the resolution of international and regional problems," said Ahmadinejad at a joint news conference with Talabani.
"The enemies of our governments have never wanted Iran and Iraq to be united, to strengthen one another. The two parties are, however, determined to intensify their political, economic and cultural co-operation," he added.
Ahmadinejad also said that his visit would open a "new chapter" in relations between the two countries. Iran recently said it is offering a $1 billion loan to Iraq for projects to be handled by Iranian firms.
The Iranian leader also met with Iraqi Prime Minister Nuri al-Maliki in the
Green Zone, the U.S.-protected central compound that is home to the Iraqi parliament and the U.S. embassy.
The U.S. is not involved in providing security for Ahmadinejad's visit and has said it will only get involved if asked for assistance.
The U.S. and Iran held three rounds of talks in Baghdad last summer, pledging to set up a three-party committee on Iraq's security and defense capabilities. They were the first direct talks between the two countries since they severed relations in 1979 following the Islamic Revolution which overthrew the U.S.-backed Shah.
Before leaving Iran for Baghdad, Ahmadinejad hit out at U.S. accusations that Teheran was aiding militants in Iraq saying, "Isn't it odd that those with 160,000 forces in Iraq accuse us of interference?"
Ahmadinejad did have one indirect piece of praise for U.S. actions in Iraq, however.
"A visit to Iraq without the dictator is a truly happy one," he said, referring to Saddam Hussein, toppled by U.S. forces in 2003, and executed by Iraqi authorities in 2006.
The Iranian leader's visit came a day before an expected U.N. Security Council vote on a third round of sanctions against Iran over its nuclear program.
Iran insists its nuclear research is for peaceful purposes. The West, however, despite a U.S. intelligence community report last year stating that Iran had abandoned attempts to build a nuclear weapon in 2003, continues to suspect that Tehran's nuclear research has military rather than civilian aims.
