Representative Mark Amodei of Nevada on Friday became the first Republican member of the House of Representatives to back the rapidly escalating impeachment inquiry — but he said he was reserving judgment on whether President Trump should be impeached.

Mr. Amodei discussed the impeachment inquiry process during a conference call on Friday with members of the news media from his home state, and in a follow-up statement issued by his office.

He said it made sense for Congress to investigate a whistle-blower’s complaint, made public on Thursday, that Mr. Trump used a July 25 phone call with Ukraine’s president to advance his personal interests, including asking him to look into unsubstantiated allegations of corruption against former Vice President Joseph R. Biden Jr. and his younger son.

On Saturday, however, he clarified his support for congressional oversight of the whistle-blower’s complaint. His office contended that was not the same as endorsing the impeachment inquiry being led by Democrats.