More than 130,000 Russian troops now staged outside Ukraine: U.S. official

Ukraine's president urged calm amid intensified warnings of a possible Russian invasion within days, saying he had yet to see convincing evidence of that, even as the U.S. reported Sunday that Moscow positioned more of its troops closer to Ukraine's borders and some airlines cancelled flights to the capital of Kyiv.

U.S. President Joe Biden spoke for about 50 minutes Sunday with Ukrainian President Volodymyr Zelensky and renewed promises of what the West says will be tough economic sanctions against Moscow and a NATO buildup in the event of "any further Russian aggression" against Ukraine, the White House said. They agreed to pursue both deterrence and diplomacy in the crisis, it added.

The U.S. updated its estimate for how many Russian forces were now staged near Ukraine's borders to more than 130,000, up from the 100,000 the U.S. has cited publicly in previous weeks. A U.S. official gave the estimate, speaking on condition of anonymity to discuss the administration's conclusion.

Zelensky's repeated statements playing down the U.S. warnings -- while Moscow's forces surround Ukraine on three sides in what the Kremlin insists are military exercises -- grew this weekend to his questioning the increasingly strident statements from U.S. officials in recent days that Russia could be planning to invade as soon as midweek.