Secretary-General Ban Ki-moon is calling for more peacekeepers to strengthen the U.N. force in conflict-wracked South Sudan, saying he is especially worried about ethnically targeted killings.

Ban did not say how many new troops and police he will request. He said he will send a recommendation later Monday to the U.N. Security Council, which must approve any increase to the force.

The U.N. has about 7,000 peacekeepers and international police in the world's newest nation.

Ban said the situation in South Sudan "is of mounting urgency," with tens of thousands of people displaced and some 45,000 seeking protection at U.N. bases.

He said he will be spending most of Monday urging regional leaders to increase military support and "political backing for efforts to defuse the crisis."