The US has agreed to deploy more than 200 additional troops to Iraq and to send eight Apache helicopters for the first time into the fight against Islamic State (IS) forces in Iraq.
It is the first major increase in US forces in nearly a year, US defence officials said on Monday.
The uptick in American fighting forces -- and the decision to put them closer to the front-lines -- is designed to help Iraqi forces as they move to retake the key northern city of Mosul.
Speaking to reporters in Baghdad, Defence Secretary Ash Carter says the decision to move US advisers to the Iraqi brigade and battalion level will put them "closer to the action".
But he says they will have security forces with them and the US will do what's needed to reduce the risks.
A senior US official said there will be eight Apache helicopters authorised to help the Iraqi forces when Iraq leaders determine they need them.
The official was not authorised to discuss the numbers publicly so spoke on condition of anonymity.
Last June, the Obama administration announced that hundreds of troops would be deployed to help the Iraqis retake Ramadi -- a goal they accomplished at the end of the year.
President Barack Obama has emphasised the additional troops won't be doing the fighting, but the extra training and intelligence support they provide can "continually tighten the noose".
"As we see the Iraqis willing to fight and gaining ground, let's make sure we're providing them more support," Obama said in an interview with CBS that aired on Monday evening.
Obama also predicted success in Mosul.
"My expectation is that by the end of the year we will have created the conditions whereby Mosul will eventually fall," he said.
Most of the additional troops will be Army special forces, who have been used throughout the anti-Islamic State campaign to advise and assist the Iraqis.
The remainder will include some trainers, security forces for the advisers, and maintenance teams for the Apaches.
The decisions reflect weeks of discussions with commanders and Iraqi leaders, and a decision by Obama to increase the authorised troop level in Iraq by 217 forces to 4087.
Carter called the addition of the Apache helicopters significant and discussed the Apaches with Iraq Prime Minister Haider al-Abadi.
Speaking to US troops at the airport in Baghdad, Carter also said that the US will send an additional long-range, rocket-assisted artillery system to Iraq.
Carter will travel to Saudi Arabia this week to meet with defence ministers from Gulf nations.
Obama will also be in Riyadh to talk with Gulf leaders about the fight against the Islamic State and ask for their help in rebuilding Ramadi, which took heavy damage in the battle.