President Trump conceded Friday that Democrats had enough votes to impeach him, but he suggested that Speaker Nancy Pelosi hold a House vote to formally begin an inquiry to force a Senate trial on whether to remove him from office.
Even as Trump boasted of a "Very unified" Republican Party that would protect him from conviction, some Republicans publicly broke ranks with him Friday.
Trump said he would spell out his complaints in a letter to Pelosi, whom Republicans have increasingly accused of short-circuiting the formal impeachment process by not holding a vote on the House floor to launch an inquiry.
House Democrats have ramped up their inquiry, interviewing key Trump administration officials and issuing subpoenas as part of their probe of the president's dealings with the Ukrainian government.
Democrats are investigating whether Trump or others in his administration linked the release of the aid to the president's request that Ukraine investigate Biden and his son Hunter.
Republicans have struggled to find a consistent defense of Trump in the wake of the whistleblower's report, which was published last week.
The anonymous whistleblower claimed that Trump pushed for the Ukrainian government to investigate his political rival, allegations that have been confirmed as the congressional probe has uncovered text messages, internal documents and sworn testimony from the Trump administration.