President Trump on Thursday called for Joe Biden and his son Hunter to testify as the president sought to deflect allegations of wrongdoing in Ukraine toward the Democratic presidential candidate.

Trump parroted a quote from Sen. John Kennedy asking what Hunter Biden does to earn money, tweeting that it was a "very good question."

"He and Sleepy Joe must testify!" Trump tweeted, using a nickname to refer to the former vice president.

Neither of the Bidens are likely to testify in the House impeachment inquiry. While Republicans have the power to request a subpoena of witnesses, those requests are subject to approval by Democrats leading the investigation.

Still, the Bidens may face more scrutiny in the GOP-controlled Senate. The Washington Post reported that Kennedy and Sen. Rand Paul (R-Ky.) were among those suggesting that the Senate summon Hunter Biden to testify about his business dealings.

Some Republican senators were uncomfortable with the strategy, The Post reported.

Trump's continued attacks on the Bidens come as the House prepares for a public phase of the impeachment inquiry, with open hearings scheduled for next week as Democrats probe the president's attempts to push foreign governments to investigate his political rivals.

Witnesses have testified in closed-door hearings that they were concerned a White House meeting for the Ukrainian president was contingent on Ukraine publicly announcing investigations that Trump and his associates wanted.

Trump has publicly urged Ukraine and China to look into the Bidens. The president has repeatedly pushed the unsubstantiated theory that Joe Biden engaged in a quid pro quo by pushing for the ouster of a Ukrainian prosecutor at the same time his son was working on the board of a Ukrainian energy company.

Hunter Biden joined the board of Burisma Holdings, a natural gas giant in Ukraine, in 2014. The company's founder was under investigation by prosecutor general Viktor Shokin, who the U.S., the United Kingdom and other Western governments argued had failed to rein in corruption in the country.

The U.S. threatened to withhold roughly $1 billion in loan guarantees if Shokin was not replaced as prosecutor general, a message Joe Biden delivered to officials in Kiev while serving as vice president and recounted during a 2018 Council on Foreign Relations conference.

The Obama administration was among multiple western governments that wanted the prosecutor general ousted.

Many of Trump's allies have argued that there was at minimum a conflict of interest at play, though the former vice president has denied acting with his son's interests in mind and there is no evidence of any criminal wrongdoing by either of the Bidens.