WASHINGTON: US Ambassador to Russia Jon Huntsman is resigning after more than two years in one of the hottest of diplomatic hot seats, a US newspaper reported Tuesday.

The Salt Lake Tribune published Huntsman's resignation letter to President Donald Trump in which he said he would leave effective October 3 to attend to family and personal demands back home.

The White House and State Department did not immediately confirm the report.

In the letter, Huntsman noted the upheaval he has witnessed in US-Russian relations during a period marked by spying accusations, scandal over Russia's alleged interference in US elections, the demise of a key Cold War nuclear missile treaty, and continuing conflict in Ukraine.

"We must continue to hold Russia accountable when its behavior threatens us and our allies. While much of what divides us is irreconcilable, there are common interests we cannot ignore," Huntsman's letter said.

"No reset or restart is going to help, just a clear understanding of our interests and values."

CNN reported that Trump and Russian President Vladimir Putin had discussed the upcoming switch in ambassador when they talked by phone last week in a conversation the White House said focused mostly on huge wildfires in Siberia.

One of Huntsman's most delicate tasks involves the case of Paul Whelan, a former US marine detained in Russia on accusations of espionage. Trump, frequently accused of cosying up to Putin, has been notably silent about Whelan's fate.

The Salt Lake Tribune said Huntsman is considering running for governor in his native Utah, a position he held previously.