WASHINGTON (Reuters) - U.S. national security adviser John Bolton said on Thursday he had great “frustration” over the fact that the conflict in Western Sahara has not been resolved.

“I’d like to see this resolved if the parties can agree on the way forward. That’s the preference,” told reporters at a Washington think tank where he laid out the Trump administration’s new Africa strategy.

U.N. talks on disputed Western Sahara ended a week ago without a breakthrough, but all sides agreed to meet again in early 2019, U.N. envoy Horst Koehler said.

U.N. efforts have repeatedly failed to broker a settlement over the desert territory, contested between Morocco and the Algerian-backed Polisario since Spain left in 1974.