Mr Obama said the additional personnel to reinforce security at the US Embassy, the Baghdad International Airport and other facilities, in light of the ongoing security situation in the country.
Extra security forces, rotary-wing aircraft as well as intelligence and surveillance support were being sent as part of the deployment.
"This force is deploying for the purpose of protecting US citizens and property, if necessary, and is equipped for combat," Mr Obama said in a letter to the speaker of the House of Representatives.
"This force will remain in Iraq until the security situation becomes such that it is no longer needed."
The Foreign Secretary has been clear on the threat of Isis, but he has ruled out the prospect of any UK military involvement in the crisis.
Iraq’s foreign minister, Hoshyar Zebari, is a natural diplomat. Polite, immaculately dressed, and blessed with a great memory.
Isis has paraded military equipment in Mosul it captured from when the Iraqi army fled in what some see as a "nightmare scenario."