SALT LAKE CITY — U.S. Ambassador to Russia Jon Huntsman Jr. has submitted his resignation, signaling the end of a two-year stint during what he called a historically difficult time in relations between the two countries.

Huntsman is planning to return to Utah amid speculation that he may again run for governor, said Salt Lake Chamber president Derek Miller, who served under him during his previous tenure.

Huntsman, a Republican, left the Utah governor’s office in 2009, when former President Barack Obama tapped him as ambassador to China. He was popular in the state and had been elected to his second term the year before.

Huntsman mounted a brief run for president in 2011. In 2017, President Donald Trump named him as ambassador to Russia, as the U.S. investigated Moscow’s meddling in the 2016 election.