BRUSSELS (Reuters) -- European countries agreed on Tuesday to respond to a UN call to help its peacekeepers in Congo during forthcoming elections, charging military planners to work out how troops could be best deployed.

A final decision is not expected until the end of the month, and planners will study options ranging from a deployment of anything from 200 to 1,250 troops, some possibly on standby.

"The European Union is keen to engage, the question is how," said an EU diplomat after a meeting of envoys in Brussels.

Another diplomat stressed that any mission would be to complement the nearly 17,000 UN peacekeepers already there. "This is not in any way about substituting for them," said the diplomat.

Britain, whose army is stretched by its 8,000-strong Iraq deployment and other military commitments, agreed on the need to provide support in Congo but would not be contributing forces itself, a British government spokeswoman said.

The United Nations asked the EU in January for a force of some 800 troops to help stabilize the Democratic Republic of Congo ahead of the first free elections since independence from Belgium in 1961. They are due to be held by June.

The world body would prefer an EU force on the ground in Congo but would accept other choices. An EU fact-finding mission to Kinshasa earlier this month concluded that a standby force on reserve outside the country might be sufficient.

Germany has denied reports it could send up to 500 troops to Congo and has made clear it would not take part unless several EU nations offered forces. France is awaiting the assessment of EU military planners before it says what role it will play.

The elections, under a constitution drafted with EU mediation last year, are meant to draw a line under five years of civil war from 1998 to 2003 during which an estimated four million people died of hunger, disease and violence.