Chinese President Xi Jinping and U.S. President Donald Trump attend a welcome ceremony at the Great Hall of the People in Beijing on November 9, 2017.

Three sources outside the administration who are close to the trade talks acknowledged Trump's request looks bad as efforts to sign an agreement continue. They also did not rule out the notoriously freewheeling Trump bringing a Biden investigation up during potential conversations with Chinese President Xi Jinping or Vice Premier Liu He. Still, they said Trump trade officials have not let concerns about Biden infiltrate talks in any formal way.

Yet Trump's push likely will not figure into official trade talks as the world's two largest economies try to strike a deal and end a damaging conflict. Discussions resume in Washington on Thursday.

The stakes are massive: the Trump administration's ongoing trade war with China has helped to fuel fears of a slowing U.S. economy, and the president sees cracking down on Beijing's alleged abuses as a domestic and foreign policy priority.

Still, Trump's comment added to the scrutiny he faces — most notably in the form of a House impeachment inquiry — over accusations he abused his power by urging Ukraine to influence the 2020 election by probing Biden, one of his top challengers for the White House. It quickly raised questions, including from House Speaker Nancy Pelosi, about whether Trump could ease up on his trade deal demands or come to an agreement with Beijing more quickly in exchange for a Biden investigation.

On Friday, a day after he said that "China should start an investigation" into the former vice president and his son Hunter, Trump himself said he would keep trade talks and his Biden concerns separate.

President Donald Trump's appeal to China to investigate his political rival Joe Biden has increased the pressure on the president at home, but it may not affect high-stakes trade talks with China in a meaningful way.

Outside experts on the economic relationship between the U.S. and China also say they doubt the trade teams will bring up the former vice president during discussions.

"It seems pretty unlikely to me that any of the negotiators would bring this up," said David Dollar, a senior fellow at the Brookings Institution and a former Treasury Department emissary to China during the Obama administration.

The renewed trade talks come at a delicate time for the Trump administration. The president has increasingly lashed out as he denies any wrongdoing in asking Ukraine and China to probe Biden. At the same time, the Trump administration's tariffs have contributed to fears about a flagging economy ahead of the president's reelection bid — though the U.S. unemployment rate just hit a 50-year low.

On Friday, Trump repeatedly claimed he did not care about Biden's political fate and only wanted to look into "corruption." (He later responded, "We'd have to look," when questioned about whether he asked foreign leaders to investigate anyone who is not his political rival.) Trump added that he would separate his desire to investigate Biden from the trade talks with China.

"One thing has nothing to do with the other," Trump said when asked if he was more likely to strike a trade deal with China if its government investigates Biden.

Speculation at times swirled that several issues, from a U.S. ban on Chinese technology company Huawei to pro-democracy protests in Hong Kong, would affect trade talks more than they eventually did, said Clete Willems, a former top trade official in the Trump administration. He said he does not think the push to probe Biden "will be a real issue in the trade talks."

Dollar also questioned why China would want to get involved in the 2020 U.S. election. He said, "I think they believe it's a minefield" to appear to be meddling.

Chinese Foreign Minister Wang Yi said as much Friday, according to the state-affiliated newspaper Global Times.

"China will never interfere in the internal affairs of the United States, and we trust that the American people are capable of sorting out their own problems," Wang said.

Global Times tweet

A Reuters report also questioned why China would share damaging information about Biden even if it had any. As Trump has taken a more aggressive stance toward China than any of his recent predecessors, Beijing may not want to take steps to help him stay in office.

Whether it ends up affecting trade talks, Trump's request for China to probe Biden has increased the criticism he faces on Capitol Hill. After Republican House Minority Leader Kevin McCarthy asked Pelosi, a Democrat, to suspend the impeachment inquiry on Thursday, Pelosi in part cited China's comments in saying she would not.

"I received your letter this morning shortly after the world witnessed President Trump on national television asking yet another foreign power to interfere in the upcoming 2020 elections," Pelosi wrote to McCarthy. "We hope you and other Republicans share our commitment to following the facts, upholding the Constitution, protecting our national security, and defending the integrity of our elections at such a serious moment in our nation's history."

Very few Republicans have yet spoken out against Trump's actions related to Biden. Still, his comments Friday explaining why he wanted to get China to probe Biden sparked perhaps the sharpest GOP critique of the president since Pelosi announced the impeachment inquiry.

"When the only American citizen President Trump singles out for China's investigation is his political opponent in the midst of the Democratic nomination process, it strains credulity to suggest that it is anything other than politically motivated," Sen. Mitt Romney, R-Utah, said in a statement Friday.

"By all appearances, the President's brazen and unprecedented appeal to China and to Ukraine to investigate Joe Biden is wrong and appalling."

— CNBC's Kayla Tausche and Tom Franck contributed to this report.

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