Citing U.S. officials, the whistleblower said "the President did not want to meet with Mr. Zelenskyy until he saw how Zelenskyy 'chose to act' in office."

Friday's letter to Pence came as the three committees said earlier on Wednesday that they would issue a subpoena to the White House to compel it to cooperate with the investigation. Trump said he would leave it to his lawyers to decide whether to comply with the congressional order.

At an event in Scottsdale, Arizona, on Thursday, Pence backed Trump's call for Ukraine to investigate the Bidens. "One of the main reasons we were elected to Washington, D.C., was to drain the swamp," he told reporters, using the same phrase Trump used in his tweets.

"My predecessor had a son who was paid 50,000 dollars a month to be on a Ukrainian board at the time that Vice President Biden was leading the Obama administration's efforts in Ukraine, I think (that) is worth looking into," Pence said, echoing Trump's request that Biden and his son Hunter Biden, who once worked for Ukrainian gas company Burisma Holdings that was accused of corruption, be investigated.

There has been no evidence so far of any wrongdoing by either Biden senior or junior.

In the latest development, the U.S. House Committee on Oversight and Reform issued a subpoena late on Friday to the White House, seeking documents related to Trump's interactions with Ukraine.

【国际英语资讯:U.S. House committees seek Ukraine-related documents from Vice President Pence】相关文章：

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