Acting US ambassador to China David Rank resigned from his post in Beijing over President Donald Trump’s decision to withdraw from the Paris climate agreement, several sources familiar with the decision told CNN.

A career foreign service officer since 1990, Rank assumed the position of deputy chief of mission at the US embassy in Beijing in January 2016 and had been serving as charge d’affaires until the arrival of Trump’s pick for the job, former Iowa Gov. Terry Branstad, who was confirmed by Congress late last month.

“Dave is exactly the type of diplomat any American would want representing their interests abroad, and he was sought after within the State Department for increasingly difficult and challenging assignments because he’s strategic, smart, savvy, curious, loyal and non-partisan,” said Dan Feldman, who worked with Rank for five years on Afghan issues.

“Given he spent much of his career seeking to strengthen the US-China relationship to benefit all Americans, we need his expertise and skills now more than ever before,” he said. “It’s heart-wrenching that we’re losing career officers of his talent, as they pride themselves on serving any administration, but some are increasingly grappling with whether they must take principled decisions as they balance their sense of duty with their conscience.”

Rank has served in several senior positions within the US State Department including time as the director of the office of Afghanistan affairs and as a senior adviser to the special representative for Afghanistan and Pakistan.

“Mr. Rank made a personal decision,” a senior State Department official told CNN, stopping short of citing the climate deal developments as the reason. “We appreciate his years of dedicated service to the State Department.”

But sources familiar with the decision indicated that Rank’s departure is directly tied to Trump’s controversial move to pull out of the accord.

One source familiar with Rank’s decision to resign said that Rank addressed his staff on Monday and talked about his four tours in China and how much he loved the country. But he said this weekend he was asked to do something which “as a parent, patriot and Christian, I simply cannot do.”

Rank, according to the source, told the embassy staff he couldn’t in good conscience do anything that would contribute to the implementation of the decision to withdraw from the climate agreement. He said he looked for a way to avoid a conflict between his duty and conscience but when he couldn’t find one, he offered to resign, assuming his resignation would be accepted. And it was accepted.

Rank was serving in China when President Xi Jinping and then-US President Barrack Obama jointly declared their commitment to the Paris agreement.

China, the world’s largest carbon emitter, said it would stick by its commitments to the treaty despite the US decision.

Rank becomes the second US diplomat serving at one of the largest embassies in the world to publicly split with Trump in recent days.

The acting US ambassador to the United Kingdom, Lewis Lukens, issued a statement on Twitter singling out London Mayor Sadiq Khan for praise after Trump attacked him on Twitter in the wake of the terror attacks which killed at least seven people.

“I commend the strong leadership of the @MayorofLondon as he leads the city forward after this heinous attack,” read a tweet from the US’ London embassy attributed to Lukens.

Trump appeared to misconstrue a statement made by Khan after the attack in London, writing on Twitter: “At least 7 dead and 48 wounded in terror attack and Mayor of London says there is “no reason to be alarmed!”

Lukens is serving as ambassador until Trump gets a permanent pick confirmed. Trump has yet to formally nominate his choice for the job, although he said prior to his inauguration that he would choose New York Jets owner Woody Johnson.