* EU hopes force will start arriving by end-February
* Force smaller than EU officials earlier suggested
* Donors pledge $500 mln for Central African Republic
By Adrian Croft
BRUSSELS, Jan 20 (Reuters) - The European Union decided on Monday to send troops to help stabilise Central African Republic, deploying its first major army operation in six years, but the force will be smaller than originally expected at around 500-strong.
The EU has been spurred into action by communal bloodshed in Central African Republic that led a senior U.N. official to warn last week of a risk of genocide there without a more decisive international response.
France, which sent 1,600 troops to its former colony last month to stop massacres between Muslim and Christian militias triggered by a March coup, welcomed the EU's move, which follows French lobbying for stronger European support for French and African efforts to halt the violence.
"This means that in cooperation with the U.N. and with the African forces, Europe will militarily support Central African Republic, as we asked," French Foreign Minister Laurent Fabius told reporters.
But Fabius said the size of the force under discussion was just 500 soldiers, smaller than the contingent of up to 1,000 soldiers that EU officials had earlier suggested could be dispatched.
Few EU countries have so far come forward with firm offers of troops, and some of the EU force could be French soldiers, EU diplomats said.
German Foreign Minister Frank-Walter Steinmeier said the EU's decision to commit troops did not mean it was "the beginning of a big engagement in Africa after Afghanistan."
More than a million people have been displaced by the violence and more than 1,000 people were killed last month alone in Bangui.
Donors at another meeting in Brussels pledged nearly $500 million in humanitarian aid for Central African Republic amid concern among aid officials at the deteriorating situation.
EU officials hope the EU force, which will be based around the capital Bangui and its airport, will start arriving in Central African Republic by the end of February.
It will stay for up to six months before handing over to an African Union (AU) force that is due to increase to 6,000 peacekeepers.
EU foreign ministers said the aim was to protect civilians and to create conditions for supplying humanitarian aid.
"We do face an emergency there and we need to act," Swedish Foreign Minister Carl Bildt told reporters.
The French troops are operating under a U.N. mandate to assist the AU force. EU officials will seek United Nations Security Council authorisation for the EU mission on Thursday.
It is not yet clear which EU countries will contribute troops. Estonia has promised soldiers, and Lithuania, Slovenia, Finland, Belgium, Poland and Sweden are among countries considering sending troops, diplomats say.
Large EU countries such as Britain, Germany and Italy have said they will not send ground troops.
The EU has 7,000 staff deployed around the world on 12 civilian missions and four military operations, including combating piracy off Somalia and training the Mali army.
But this will be the EU's first land operation since it sent a force to eastern Chad and northeastern Central African Republic in 2008 as part of regional efforts to deal with the Darfur crisis in Sudan, an EU official said. (Additional reporting by Tom Koerkemeier; Editing by Mike Collett-White)