Iranian President Mahmoud Ahmadinejad has said the presence of foreign forces in Iraq is a humiliation and an insult to the region.
Mahmoud Ahmadinejad signed a number of co-operation deals
On the second day of a visit to Iraq, he said major powers should not be interfering in the region's affairs.
Mr Ahmadinejad called for the immediate withdrawal of foreign troops.
It is the first-ever visit to Iraq by an Iranian president. The two countries fought an eight-year war when Saddam Hussein invaded Iran in 1980.
Mr Ahmadinejad did not mention the US by name, but Washington still has more than 150,000 soldiers based in Iraq, nearly five years after it led the 2003 invasion.
The Iranian president and his Iraqi counterpart, Jalal Talabani, on Monday signed a number of co-operation agreements on trade and transport.
"Without the presence of the foreign troops the region will live in peace and brotherhood," Mr Ahmadinejad said.
"We believe that the forces that came from overseas and travelled thousands of kilometres to reach here must leave the region, and must hand over responsibility to people of the region," he said.
Mr Ahmadinejad made these comments in response to questions from Iraqi and foreign journalists.
BBC Baghdad correspondent Jim Muir says Mr Ahmadinejad's comments did not amount to a strident call for an immediate American withdrawal.
HAVE YOUR SAY
This is a historic opportunity for Iraq and Iran to bury the venom of the past.
Rajendra Aneja, Dubai, UAE
He knows his Iraqi hosts are about to negotiate a long term strategic accord with the US that would keep troops here long enough to ensure the Baghdad government's survival against both internal and external threats.
Our correspondent says Mr Ahmadinejad's visit could not contrast more strongly with those of Iraq's only other presidential visitor since the overthrow of Saddam Hussein, President Bush, whose trips have been unannounced, brief and confined to American military bases.
Mr Ahmadinejad arrived in Iraq on Sunday.
He accused the US of bringing terrorism to the region, called on Washington to change its standpoint towards Iran and said it had to understand that the Iraqi people did not like the US.
US officials have often accused Iran of supporting militants operating in Iraq.
The Iranian leader is due to end his visit on Monday.
Iraqi leaders extended a warm welcome to the Iranian president on Sunday.
After talks with Mr Talabani, Mr Ahmadinejad said the visit had opened a "new page" in Iran-Iraq relations.
Prime Minister Maliki said his talks with Mr Ahmadinejad had been "friendly, positive and full of trust".
Despite the reconciliation between Baghdad and Tehran, many analysts believe that in the long term, the two countries are destined to be rivals for regional power.
During the long war between them in the 1980s, many of the prominent Shia now in positions of power in Iraq fled to Iran as Saddam Hussein cracked down on internal dissent.
The US-led overthrow of Saddam Hussein's regime allowed them to return from exile.
Trade is now growing between the two countries and tourism, in the form of Iranian pilgrims visiting major Shia shrines in Iraq, is booming.