"One hundred and twenty troops from the Second Light Infantry will be sent this weekend. They are currently based in Cyprus," a ministry spokesman said.
The decision marks the start of a larger scale reinforcement of British troops in the war-ravaged country, after a report last week urged more deployments to avoid “strategic failure.”
The Government is to send several thousand more troops to Iraq over coming weeks though the full brigade-level force of 5,000 which the Foreign Office wanted cannot be sent because commanders do not have enough easily deployable troops available.
Britain's military force in Iraq currently numbers 10,500 troops. Most of these are in the south of the country around the port city of Basra.
Pressure from Straw
The decision to send troops, which will likely be announced by Defence Secretary Geoff Hoon in Parliament on Monday follows pressure from the Foreign Minister Jack Straw.
Straw told Prime Minister Tony Blair on Wednesday that the UK must demonstrate the allies' commitment to Iraq.
"Only the UN can bring in other nations, restore Iraq's sovereignty and command legitimacy"
British Liberal MP
He sees it as the only way to persuade the US to add to its own numbers in the face of a campaign by Saddam Hussein loyalists that has claimed the lives of 67 American and 11 British soldiers.
A company from 2nd Battalion, the Light Infantry, based at Dhekelia, Cyprus, will depart this weekend, while 1st Battalion, the Light Infantry will arrive in Iraq at some point next week, the Ministry of Defence said.
Dearth of soldiers
The British Army is suffering a dearth of easily deployable soldiers as many are on leave after having spent substantial periods of time on active duty in either Iraq, Afghanistan, the Balkans or Sierra Leone.
That has disrupted the “formation readiness cycle,” the Daily Telegraph reported, which ensures soldiers get the right mix of training, maintenance and time off.
In an about turn, US Secretary of Defence Donald Rumsfeld on Friday admitted that he may have to boost US troop numbers by as much as a division - some 15,000 soldiers.
British opposition Liberal Democrat defence spokesman Paul Keetch applauded the news that British troops would be reinforced though added that the situation in Iraq could not only be bettered by sending more soldiers.
"It is all very well Britain sending more troops, but what is really needed to build security in Iraq is a broad international consensus backed up by United Nations authority.
"Only the UN can bring in other nations, restore Iraq's sovereignty and command legitimacy."
Meanwhile, members of the United Nations Security Council were Saturday due to continue reviewing a US proposal which allows for an increased UN role in Iraq.
Both France and Germany have demanded a timetable for an end to US occupation
The US draft resolution calls for a UN multinational force in Iraq and offers the UN a role in writing a constitution leading to elections.
Still many countries, in particular France, Germany and Russia, are wary of the proposal which would leave the US in ultimate control.
France, German opposition
Having initially opposed the war, they suspect the US is seeking to pass on to others the mess they have inherited in Iraq.
French President Jacques Chirac and German Chancellor Gerhard Schroeder have harshly criticised the US resolution and have demanded a timetable for the US occupation to end.