DES MOINES, Iowa -- It may seem odd for the governor of a lightly populated agricultural state to be chosen as U.S. ambassador to China, especially amid escalating talk of a trade war with the major U.S. trading partner.

But Iowa Gov. Terry Branstad boasts a 30-year relationship with Chinese President Xi Jinping, the most powerful Chinese leader in decades.

"Given Xi's penchant to keeping things close-hold, it is important for the U.S. to have a reliable and direct communication channel to him," said Bonnie Glaser, senior adviser for Asia at the Center for Strategic and International Studies. "Branstad has met Xi periodically since 1985 and has a personal relationship with him that could be very useful."

This relationship, begun when both men were political upstarts, could be put to the test in coming months if Branstad is confirmed.

President-elect Donald Trump, who announced his choice of Branstad on Wednesday, said during the campaign that his administration would make closing the U.S. trade deficit with China a top priority. Through the first 10 months of the year, government figures show the United States is running a $288.8 billion deficit with China on the trade of goods, a sharp decline from the same time a year ago.

But Trump has suggested imposing 45 per cent tariffs on Chinese products and has labeled the country a "currency manipulator." Chinese officials have warned that the U.S. is bound by World Trade Organization rules, which restrain countries from imposing sanctions without making a persuasive case.

In that way, Trump's selection of Branstad appears to be savvy.

Patrick Cronin, senior director of the Asia-Pacific security program at the Center for a New American Security, said that by selecting an ambassador who has forged commercial ties between his state and China, Trump was signalling to Xi that as leaders they will have the same fundamental priority in seeking economic growth.

In 1985, Branstad was nearing the end of his first term as governor, then the nation's youngest at age 39. Xi was a rising leader seeking ideas in Iowa for crop and livestock techniques to help his own agriculturally rich region.

In 2013, he returned to Iowa as China's incoming president and met with Branstad for a formal dinner in Des Moines between meetings in Washington with President Barack Obama and a trip to California.

If Trump's threats suggest the U.S.-China relationship could be bumpy, Branstad's longtime relationship with Xi could help smooth things. His personal touch could go a long way in avoiding conflict caused by miscommunication or misinterpretation.

Trump angered China by speaking to Taiwan's president last week in a breach of diplomatic protocol. China still regards the island as part of its territory and would consider it unacceptable for the U.S. to recognize Taiwan's leader as a head of state.

China's state-run news agency Xinhua said in a Thursday commentary that Branstad's appointment is a "positive signal sent amid a mixture of messages from Trump," a reference to Trump's call with Taiwan leader Tsai Ing-wen and his criticism of China on trade and geopolitical issues.

At a daily news briefing on Thursday, Chinese Foreign Ministry spokesman Lu Kang said China considered the position of U.S. ambassador to Beijing to be "an important bridge" and that "Governor Branstad is an old friend of the Chinese people."

Cronin said he wouldn't overstate the importance of the role of an ambassador in the modern era or the depth of Branstad's personal ties with Xi. "I don't think anyone is a drinking buddy of Xi Jinping, but familiarity is useful and could advance U.S. diplomacy," he said.

Branstad's rapport with Xi could also outweigh the courtly, 70-year-old Midwesterner's lack of formal diplomatic experience, though he has made multiple trips to China to pitch Iowa's robust harvests, as recently as last month.

Knowing the Chinese leader personally is even more important than it might have been in the past. Previous Chinese leaders ruled by consensus, but Xi has consolidated power in his hands, ousting rivals in an anti-corruption campaign and taking on responsibility for economic policy, typically the purview of the government's No. 2 official, now Li Keqiang.

Republican Sen. Marco Rubio appeared to criticize the choice Wednesday, calling for the Trump administration to press China's government and ruling Communist Party to respect human rights and uphold the rule of law.

"It is my hope that this new administration will appoint an ambassador to China that reflects these priorities, not simply someone who is going there to catch up with old friends," Rubio said without mentioning Branstad by name.

Trump, who met with Branstad Tuesday in New York, travels Thursday to Iowa.

Pennington reported from Washington. Christopher Bodeen and Gerry Shih in Beijing contributed to this report