President Trump is ending a covert CIA operation to arm and train Syrian rebels fighting against President Bashar al-Assad, something Russia has long desired, according to a Wednesday report in the Washington Post.

The Obama administration introduced the operation in 2013, as a part of its efforts to push Assad out of power, and its effectiveness has come into question even among its backers. But the timing of the decision raises questions for the White House, as it fends off accusations that the president and his team obscured his interactions with Russian President Vladimir Putin at the G-20 summit in Hamburg, Germany, earlier this month.

On Tuesday, the White House admitted the president had a previously undisclosed discussion with Russian President Vladimir Putin over dinner at the G-20. White House deputy press secretary Sarah Huckabee Sanders on Wednesday declined to tell reporters during a briefing what Putin and Mr. Trump discussed. The White House is also working to explain the growing list of attendees at the June 2016 meeting Donald Trump Jr. held with a Russian lawyer and others at Trump Tower.

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Russia has been critical of U.S. efforts to punish Assad, particularly after the deadly chemical attack Assad carried out on his own people in April. Mr. Trump retaliated against that attack by ordering a missile launch on a Syrian airbase.

Mr. Trump struck a deal with Russia at the G-20 summit on a ceasefire in southwest Syria. Mr. Trump said the deal was a benefit of working with Moscow.

Some members of the Trump administration have been clear Assad cannot remain in power. In April, Secretary of State Rex Tillerson said Assad has "no role" in governing Syria long term. Nikki Haley, U.S. Ambassador to the United Nations, at the time said "in no way" can there be peace in that region of the Middle East while Assad is in charge.

The CIA program, according to the Washington Post report, will be phased out gradually.