Maliki, speaking to the Wall Street Journal, said the new Iraqi government and the country's security forces were capable of confronting any remaining threats to its security, sovereignty and unity.
"The last American soldier will leave Iraq" as agreed, he said, speaking at his office in a leafy section of Baghdad's protected Green Zone. "This agreement is not subject to extension, not subject to alteration. It is sealed."
The remarks came amid speculation among some Iraqi and US officials that the US troop presence would eventually be extended, especially due to the recent political stalemate in the country following allegations of fraud in the election process which delayed the formation of government for nine months in the country.
Security is the new government's top priority, Maliki said, as in his previous term.
He said the only way for any of the remaining 50,000 or so American soldiers to stay beyond 2011 would be for the two nations to negotiate - with the approval of Iraq's parliament - a new Status of Forces Agreement, or SOFA, similar to the one concluded in 2008.
That deal took a year of protracted negotiations in the face of vehement opposition from many among Maliki's own Shiite constituency, and no repeat is expected.
A senior official in President Barack Obama's administration said Washington was "on track" to withdraw all its remaining soldiers in Iraq by the end of next year.
That's the final milestone in the security agreement, following the reduction in American troop levels to below 50,000 in August and the pullout of US soldiers from most Iraqi inner cities in June 2009. "The prime minister is exactly right," said the senior official.