AUGUSTA, Maine (AP) Republican Sen. Susan Collins of Maine says “it’s not OK” for a president to encourage a foreign state to investigate a political rival.

She responded to a question Saturday by saying Trump made a “big mistake” in asking China to investigate Democratic presidential candidate Joe Biden and his son. She called it “completely inappropriate.”

Collins’ comments on Saturday followed a firefighter memorial service in Maine.

Two other Republican senators, Mitt Romney of Utah and Ben Sasse of Nevada, criticized the president’s comments that further fueled an impeachment inquiry.

Collins reiterated that she would not comment on evidence that could be used in an impeachment proceeding since she could serve as a juror. She said she hopes the process is “done with the seriousness that any impeachment proceeding deserves.”