The White House said Monday that the guarantee had been provided by the Iraqis in a diplomatic note to Washington.
The failure of Iraq’s parliament to endorse a Status of Forces deal with Washington led to the complete exodus of all American troops from Iraq at the end of 2011.
Many of Obama’s political opponents say their exit fostered a power vacuum which the Sunni group Islamic State of Iraq and the Levant (ISIL) has exploited in a rapid advance across the country.
“The commander in chief would not make a decision to put our men and women in harm’s way without getting some necessary assurances,” White House spokesman Josh Earnest said.
“We can confirm that Iraq has provided acceptable assurances on the issue of protections for these personnel via the exchange of diplomatic note.”
Obama last week announced the dispatch of up to 300 advisors to Iraq to assess the needs of the country’s forces as they struggle to contain the advance of the Islamist fighters.
Earnest said the current situation differed from prevailing conditions at the end of 2011, making the less formal assurance of legal protections from Iraq more acceptable.
“We’re dealing with an emergency situation … there is an urgent need for these advisers to be able to do their work on the ground in Iraq,” he said.
Earnest said the number of advisers contemplated for this mission was much smaller than the several thousand that had been contemplated for a post-Iraq force.
The new agreement struck with Baghdad via diplomatic note is far less sweeping and appeared far less formal than the SOFA. But the U.S. government said the assurances were enough, given the scope and size of the mission.
“With this agreement, we will be able to start establishing the first few assessment teams,” said Rear Admiral John Kirby, a Pentagon spokesman. The Pentagon said on Friday the first teams would be drawn from forces already in Iraq under the U.S. embassy mission, and that additional teams would arrive from outside the country shortly after.
State Department spokeswoman Marie Harf said the agreement would give protections similar to the ones already enjoyed by U.S. diplomatic personnel in Baghdad.
“Our troops will have the legal protections they need to perform their mission,” Harf said.
“They would, were something to arise, face due process for violations under the Uniform Code of Military Justice.”
Secretary of State John Kerry, who met Iraqi Prime Minister Nuri al-Maliki in Baghdad on Monday, said U.S. support for Iraqi security forces will be “intense and sustained” to help them combat the Islamist insurgency that has swept through the country’s north and west.