BUJUMBURA, Nov 18 (Reuters) - Burundi said on Friday U.N. troops would begin withdrawing in January, after fulfilling much of their peacekeeping mission in a country emerging from a 12-year civil war that killed some 300,000 people.

Burundi's Foreign Minister Antoinette Batumubwira said up to 40 percent of the U.N.'s 5,500 blue helmets could be gone by April, according to recommendations made by a joint commission representing the government and United Nations.

Batumubwira said a decision on how the remaining U.N. troops would be withdrawn would be made in March.

She said U.N. soldiers would remain in three provinces bordering Democratic Republic of Congo where Burundi's last rebel group, the Forces for National Liberation (FNL), is still active.

"Apart from controlling security at the Burundi frontier with Congo, peacekeepers who will stay in Burundi will be dealing with the protection of ONUB (U.N.) personnel, demining operations, disarmament and resettlement of former combatants," Batumubwira told a news conference.

The FNL said on Thursday it was ready to talk peace with rebel-turned-president Pierre Nkurunziza's government for the first time, provided its imprisoned members were set free.

The 3,000-strong group had previously rejected calls for talks by Nkurunziza, and analysts say lasting peace cannot be achieved in the tiny coffee-growing country unless the FNL disarms.

A U.N. Security Council delegation visited Burundi last week to assess progress since August elections produced an ethnically-mixed government.

The vote was held under a U.N.-backed plan to end the war between Hutu rebels and a Tutsi elite which controlled the state for most of the years since independence in 1962.

The government has said U.N. operations in Burundi should shift their focus away from peacekeeping to more urgent needs like education and health.

The mandate for the U.N.'s operation in Burundi is up for renewal in December.