Major world and regional powers are to discuss ways of combating violence in Iraq, on the second day of a two-day summit in Egypt.
Iran has issued a strong attack against US policy in Iraq, blaming the American presence there for sectarian violence.
Iraq's neighbours, including Iran and Syria, will join ministers from the G8 nations and the EU in Sharm el-Sheikh.
Iran's Foreign Minister Manouchehr Mottaki was speaking at a summit of world and regional powers in Egypt, called to discuss Iraq's security.
The US has accused Iran and Syria of allowing foreign fighters to enter Iraq and of fomenting unrest in the country.
The summit had been expected to see the first high-level talks between the US and Iran in almost three decades.
The US secretary of state met Syria's foreign minister on Thursday, the highest-level talks for several years.
But the strength of the comments was likely to dash those chances, says the BBC's Sadeq Saba at the summit.
The UK foreign secretary briefly met Iran's foreign minister as well, but there was no meeting between US and Iranian officials.
'Accept responsibility'
Diplomatic push
Iraq's neighbours, including Iran and Syria, had joined ministers from the G8 nations and the EU at the conference in Sharm el-Sheikh.
More than $30bn (£15bn) in aid and debt relief was pledged by donors on the first day of meetings, which ended with the signing of a five-year International Compact for Iraq (ICI).
Speaking at the summit, Iraqi Prime Minister Nouri Maliki called for neighbouring countries to stop funding terrorists and to block their entry into the country.
The United States must accept the responsibilities arising from the occupation of Iraq, and should not finger point or put the blame on others Manouchehr MottakiIranian foreign minister
The BBC's Ian Pannell, in Sharm al-Sheikh, says the conference is the largest diplomatic push since Iraq was invaded.
"We will not allow terrorist organisations to use Iraqi territory as a safe haven," Mr Maliki said.
Iraqi Finance Minister Bayan Jabor said Egypt had agreed to write off all the money it was owed by Iraq - about $800m - while Slovenia, Bulgaria and Poland would cancel 80% of Iraq's debts.
"That is what drives us to call on the regional neighbours to prevent the infiltration of terrorist groups into Iraq and to stop them obtaining material support and political and media support."
He said the European Union had pledged $200m in grants, while British Foreign Secretary Margaret Beckett committed the UK to the same amount.
The US has previously accused Iran and Syria of allowing foreign fighters to enter Iraq and of fomenting unrest in the country.
"In return Iraq will have to commit to finding real national reconciliation," Mr Jabor told Reuters.
Mr Mottaki said the US should issue a clear troop-withdrawal plan to return stability to Iraq.
'Making progress'
"The continuation of, and increase in, terrorist acts in Iraq originates from the flawed approaches adopted by the foreign troops. Thus, in our view, the continuation of occupation lies at the origin of the crisis," he said.
Friday's discussions on security will expand on topics addressed during the brief meeting between US Secretary of State Condoleezza Rice and Syrian Foreign Minister Walid Muallem.
"The United States must accept the responsibilities arising from the occupation of Iraq, and should not finger point or put the blame on others."
Ms Rice raised US concerns over Syria's porous border with Iraq and asked Syria to stem the flow of arms and foreign fighters.
Earlier, a US military spokesman in Iraq said there had been a reduction in the number of foreign fighters crossing from Syria to Iraq in recent months.
Speaking at a news conference with the Egyptian foreign minister on Thursday, Iraqi Prime Minister Nouri Maliki said his country was making progress on security issues.
"Any rational observer of the Iraqi scene would agree that our capabilities to confront terrorism are growing day by day at the level of the army, the people and the police," he said.
"This compact which has been signed will help Iraq [fight terrorism] at the political, economic and security levels."
