WASHINGTON — President Trump is expected to name John Sullivan, the deputy secretary of state, to be the next ambassador to Russia, replacing Jon Huntsman Jr. as his liaison to Moscow, a senior administration official said. The post of ambassador to Moscow is a prestigious diplomatic position that is always challenging, but even more so after a two-year federal investigation into the Trump campaign’s possible ties to the Kremlin.

Mr. Sullivan has been confirmed once by the Senate. Should Mr. Trump move ahead with his appointment, he will face a new hearing.

Speaking on Tuesday to reporters in the Oval Office, Mr. Trump said that Mr. Sullivan “could very well be” his choice for ambassador to Moscow. The president added that Mr. Sullivan was “somebody that’s being put up” and that Secretary of State Mike Pompeo “likes him very much.”

The role is particularly delicate given the frenzy over questions about Mr. Trump’s links with Russia, dating to the 2016 campaign and his years as a businessman, and the president’s continued efforts to build a working relationship with President Vladimir V. Putin despite Russia’s aggressive actions around the world, including attempts to interfere with elections in the United States.