Acting US Ambassador to Ukraine Bill Taylor arrives for a deposition in the House Impeachment inquiry on Capitol Hill in Washington, DC, October 22, 2019.

A top diplomat testified Tuesday in the impeachment inquiry into President Donald Trump after House Democrats issued a subpoena to him following State Department attempts to block his appearance, an official working on the probe told NBC News.

Acting U.S. Ambassador to Ukraine Bill Taylor appeared Tuesday morning on Capitol Hill for a scheduled deposition in the House impeachment investigation. His text messages with other administration officials — shared with lawmakers by former U.S. special envoy to Ukraine Kurt Volker as part of the inquiry — have helped fuel suspicions that the Trump administration was trying to arrange a politically motivated quid pro quo with Ukraine.

"In light of an attempt by the State Department to direct Ambassador William Taylor not to appear for his scheduled deposition, and efforts by the State Department to also limit any testimony that does occur, the House Intelligence Committee issued a subpoena to compel his testimony this morning," an official working on the impeachment probe told NBC on Tuesday morning.

"As is required of him, Ambassador Taylor is now complying with the subpoena and answering questions from both Democratic and Republican Members and staff," the official said.