DANANG, Vietnam -- President Trump will not have a formal sit-down with Russian President Vladimir Putin while the two attend a summit, the White House said Friday shortly before Mr. Trump landed in Vietnam, the fourth stop on his first official visit to Asia.

Speaking to reporters aboard Air Force Once, White House press secretary Sarah Huckabee Sanders blamed scheduling conflicts on both sides for the fact that the leaders will not meet formally during the Asia-Pacific Economic Cooperation summit taking place in the coastal city of Danang.

But Sanders said it was "possible" and "likely" that they could have a less formal encounter, either in Danang or later in the Philippines when Mr. Trump and Putin attend another regional conference.

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"Now, they're going to be in the same place. Are they going to bump into each other and say hello? Certainly possible and likely," she said. "But in terms of a scheduled, formal meeting, there's not one on the calendar and we don't anticipate that there will be one."

Sanders spokes to reporters minutes before Air Force One landed in Da Nang.

The Reuters news agency reports Moscow says it's been getting contradictory signals from the U.S. on a possible meeting in Vietnlam. Kremlin spokesman Dmitry Peskov said Friday Putin would meet Mr. Trump on the sidelines of APEC summit in Vietnam "one way or another."

U.S. Secretary of State Rex Tillerson had told reporters in Beijing on Thursday that there was no reason to schedule a meeting if the U.S. and Russia are unable to make significant progress on issues including Syria and Ukraine.

"The view has been if the two leaders are going to meet, is there something sufficiently substantive to talk about that would warrant a formal meeting," he said.

APEC is the first of multiple summits Mr. Trump will attend on his first trip to Asia as president.