The US will send thousands of additional troops to the Middle East after President Donald Trump ordered the airstrike that killed one of Iran's most powerful men.

After hundreds of protesters targeted the US Embassy compound in Baghdad earlier this week, the US sent in 750 troops from the Immediate Response Force of the 82nd Airborne Division and said additional deployments were possible.

The new deployment will encompass the rest of the brigade -- about 3,000 soldiers.

Trump's administration has insisted that the strike was ordered to thwart an imminent threat from Iran -- not to start a war. But Democrats say the strike will increase threats to US interests from across the Middle East.

"Today the administration announced we're sending 3,000 more troops to the region," said Democratic Sen. Chris Van Hollen of Maryland.