The troops will begin arriving in the next few weeks to replace Spain's 1432-strong military contingent when they leave Iraq a month from now, said the Sunday Telegraph, a newspaper known for its connections to Britain's military establishment.
British Prime Minister Tony Blair took the decision to send the additional troops to Iraq after meeting US President George Bush at a White House summit two weeks ago, it said on Sunday.
Najaf - which contains the most important Shia shrine in Iraq - is where Shia leader Muqtada al-Sadr has established thousands of militia forces vehemently opposed to the
The British force will be composed of troops from the Royal Marine Commandos, a Parachute Regiment battalion and an unidentified infantry battalion, the Sunday Telegraph said.
Told to prepare
"Not sending troops was never really an option because of the message it would have sent to the coalition," said a senior defence ministry official quoted in the newspaper.
"It is difficult to predict how long these troops will have to remain in Iraq, but it won't be less than two years," the source said.
"Plans have been drawn up for the deployment of at least three battle groups and a brigade headquarters to Iraq.
"Officially, no decisions have been made on troop numbers, but privately units are already being told to prepare for operations," said the unnamed defence ministry official.
Britain already has 7900 soldiers operating in southern Iraq.