U.S. Ambassador to China Terry Branstad will step down and leave China in early October, the U.S. embassy said on its website on Monday in an unexpected move.

His departure leaves the U.S. mission in Beijing without a confirmed ambassador at a time when the two countries are at odds over issues ranging from the national security law for the Hong Kong Special Administrative Region to the handling of coronavirus and the South China Sea issues.

Branstad, previously the longest-serving governor of Iowa, will work on President Donald Trump's re-election campaign, Reuters reported citing a U.S. official familiar with the matter. 

The Chinese foreign ministry called Branstad "an old friend of China" when he was nominated for the ambassadorship in 2016. When asked on Monday about Branstad's departure, a foreign ministry spokesman noted the announcement on Twitter and said the Chinese side has not yet received notification about the end of the ambassador's tenure.

"It's highly unexpected he will be leaving in October," current affairs commentator Einar Tangen said. "It leaves China and the U.S. without a direct communication line."

Tangen speculated that Branstad was brought in because he met Chinese President Xi Jinping back in 1985 and they had taken up a friendship, and Trump thought Branstad could be helpful in smoothing over relations with China. 

"Trump seems to want to shock. He's constantly coming up with new ways of taking up space in the media. There's two parts to that. One, any attention that is being paid to his moves overseas against China is part of this O'Donnell & Associates strategy, which is all about bashing China, not defending his moves. And second of all, it allows him to eat up space so that people aren't concentrating on his handling of COVID-19, both the health and economic effects," Tangen went on to say.

The political commentator added that the upcoming "win-at-all-costs" U.S. election is also complicating matters. 

(Cover: U.S. President-elect Donald Trump shakes hands with Governor of Iowa Terry Branstad (L) at the USA Thank You Tour event at the Iowa Events Center in Des Moines, Iowa, U.S., December 8, 2016. /Reuters)