The UN has begun talks with the Democratic Republic of Congo on withdrawing its peacekeeping mission - the biggest UN operation in the world.

UN peacekeeping chief Alain Le Roy said his officials would take a month to assess how the pullout of 20,500 personnel could be carried out.

The current mandate of the mission, known as Monuc, expires in May.

UN troops have a mixed record in DR Congo, with accusations of sex abuse, gold smuggling and running from rebels.

The peacekeepers were first sent to the country in 1999 in a bid to calm a raging conflict dubbed "Africa's first world war".

The conflict drew in six other countries and left an estimated four million people dead.

The fighting officially ended in 2003, but parts of the east of the country remain extremely volatile.

The BBC's Thomas Fessy in Kinshasa says no details have been given on a timeline for withdrawal, but the Congolese authorities have asked for it to be carried out in one year.

Our correspondent says it is quite clear that President Joseph Kabila does not want to have a UN force in his country when a presidential election is held in late 2011.

Debate due

Mr Le Roy announced the pullout talks after a meeting with Mr Kabila, saying a UN team had been given one month to assess how the mission could start withdrawing.

The UN Security Council is due to debate Monuc's mandate next month.

Congolese government spokesman Lambert Mende told the BBC that there should be no UN troops in DR Congo other than in the troubled eastern regions of North and South Kivu by the end of this year.

"Withdrawal must be completed by mid-2011," he said.

Despite ongoing military operations in different parts of the country, the Congolese authorities want the timeline of the withdrawal to be clearly announced before 30 June, when the country celebrates 50 years of independence.

Last year, Monuc was accused of working with Congolese troops who had committed human rights abuses.

The UN peacekeepers are supporting Congolese troops in operations against Rwandan rebels based in eastern DR Congo.

In previous years, many Congolese have accused the UN of not protecting eastern towns from advancing rebel forces - but the UN has said that was not part of its mandate.