The US is to send 1,500 more non-combat troops to Iraq to boost Iraqi forces fighting Islamic State (IS) militants, nearly doubling the US presence.
The Pentagon said the troops would train and assist Iraqi forces.
President Barack Obama authorised the deployment following a request from Iraq's government, the Pentagon added.
IS militants control large areas of Iraq and Syria but have been targeted by hundreds of air strikes by a US-led coalition since August.
The 1,500 additional US troops will join the 1,600 military advisers that are already in Iraq to assist the country's army.
A statement from the Pentagon said the troops would be establishing several sites to train nine Iraqi army and three Kurdish Peshmerga brigades.
The US military would also be setting up two "advise and assist operations centres" outside Baghdad and the northern city of Irbil, the statement added.
"US troops will not be in combat, but they will be better positioned to support Iraqi security forces as they take the fight" to IS, White House spokesman Josh Earnest told reporters.
He said President Obama would also be asking Congress for $5.6bn (£3.5bn) to support the ongoing operations against IS fighters in both Iraq and Syria.
The announcement came hours after Mr Obama met congressional leaders in Washington for the first time after the Republicans won control of the Senate in Tuesday's elections.
Analysis: Tom Esslemont, Washington Correspondent
In the eyes of the Pentagon, the Iraqi armed forces are responding well to the training they have already been given.
Its spokesman Rear Admiral John Kirby said they had "stiffened their spine". So the expansion of the training programme to the north, south and west of Iraq is designed to build on what is being labelled as progress.
But others may see this deployment differently. There are those who recall how, earlier this year, the US-trained and equipped Iraqi armed forces simply crumbled in the face of Islamic State militants.
Rear Adm Kirby blamed the previous Iraqi government for that, and said that the Iraqis were now making gains and that the situation was completely different this time.
The Obama administration has said its aim was to "degrade and ultimately destroy" Islamic State militants, who control large parts of the country after launching an offensive in the north in June.
A US-led coalition has launched more than 400 air strikes on the group in Iraq since August, and more than 300 across the border in Syria.
The strikes have destroyed hundreds of the group's armed vehicles and several of its bases, but Islamic State has continued its campaign to establish a caliphate.
Last week, officials in Iraq's western Anbar province said IS militants had killed at least 322 members of a Sunni tribe who had tried to resist the jihadists.