U.S. President Donald Trump's national security adviser John Bolton said on Friday that U.S. sanctions against Russia would remain in place until Moscow changes its behaviour.
Speaking at a news conference in Kiev, Bolton added he had told Ukrainian President Petro Poroshenko that Moscow should not meddle in Ukraine's presidential vote next year.
Washington has imposed economic sanctions against Russia over its alleged meddling in the 2016 U.S. presidential election. Moscow denies the allegations.
John Bolton also said that Washington would not weigh in on an idea to swap territory between Serbia and Kosovo following Belgrade’s idea of settling a dispute that has hindered both Serbia's and Kosovo's ambitions to join the European Union by redrawing the border between the country along ethnic lines.
"Ukraine had made progress in its efforts to join the North Atlantic Treaty Organisation (NATO), but that it still had more work to do", he added.
Bolton said it was important to resolve the Ukraine crisis and that it would be dangerous to leave the situation as it is in Crimea and eastern Ukraine where Moscow has backed separatists in a conflict against Kiev.