US President Barack Obama has ordered about 350 more troops to Baghdad to protect the US Embassy in the Iraqi capital and is sending top officials to the Middle East to "build a stronger regional partnership" against Islamic State militants, the White House says.
Pentagon Press Secretary Rear Admiral John Kirby added that the move would bring the total number of US military personnel responsible for bolstering diplomatic security in Iraq up to about 820.
Obama left Washington on Tuesday (local time) to visit Estonia and then attend a NATO summit in Wales.
The White House said Obama would be consulting this week with NATO allies on additional actions to take against Islamic State forces and "to develop a broad-based international coalition to implement a comprehensive strategy to protect our people and to support our partners" against the group. The Sunni Muslim militants have captured parts of Iraq and Syria.
As part of that effort, the White House said, the United States would send Secretary of State John Kerry, Defense Secretary Chuck Hagel and Obama's counterterrorism adviser, Lisa Monaco, to the Middle East "in the near-term to build a stronger regional partnership."
The White House announcement came on the day Islamic State released a video purporting to show the beheading of a second American hostage, journalist Steven Sotloff, raising the stakes in its confrontation with Washington over US airstrikes on its insurgents in Iraq.
"The President has made clear his commitment to doing whatever is required to provide the necessary security for US personnel and facilities around the world," White House spokesman Josh Earnest said in a statement.
"The request he approved today will allow some previously deployed military personnel to depart Iraq, while at the same time providing a more robust, sustainable security force for our personnel and facilities in Baghdad," Earnest added.