SEOUL - A top U.S. defense official says Washington will not be alone if it needs to take action in response to Russia's massive troop buildup along its border with Ukraine.

Defense Secretary Lloyd Austin, in Seoul for meetings with South Korean officials, said Thursday that while he would not speculate on how Washington will respond to Russia's provocations against Ukraine, Moscow should know the U.S. will not be alone.

"Whatever we do will be done as a part of an international community," Austin said during a news conference with his South Korean counterpart, further calling on Russian President Vladimir Putin to "lower the temperature in the region."

"The best case, though, is that we won't see an incursion," the U.S. defense secretary added, noting Russia's "substantial" troop presence in the border areas is only part of the problem.

"We also see troubling rhetoric, rhetoric in the info space," Austin said. "We've heard President [Volodymyr]Zelenskiy expressed concern about efforts to undermine his administration."

U.S. Secretary of State Antony Blinken, meeting with NATO counterparts in Latvia Wednesday, warned the U.S. was preparing to ratchet up economic sanctions against Moscow, if needed.

"We've made it clear to the Kremlin that we will respond resolutely, including with a range of high-impact economic measures that we have refrained from using in the past,' he said.

Blinken is scheduled to meet with Russian Foreign Minister Sergey Lavrov later on Thursday in Stockholm.

Ukrainian officials have said Russia has positioned at least 90,000 troops along the border and in Crimea, which Moscow seized illegally in 2014.

But Russian officials have accused Ukraine of conducting its own military build up.

Earlier this week Russian President Vladimir Putin also repeated concerns about U.S. and NATO exercises in the Back Sea, and warned NATO against installing what he described as "strike systems" on Ukrainian soil.

'What are we to do in such a scenario? We will have to then create something similar in relation to those who threaten us in that way," he said at an investment forum in Moscow. "We can do that now.'

Information from Reuters was used in this report.