Mr. Trumka said the president had been generous with access to the Oval Office and administration officials, and he described Mr. Trump as “charming person to person.” One meeting scheduled to last 30 minutes went on for nearly three hours, he said.

But those meetings, and the president’s affability, failed to yield results, Mr. Trumka said: “Access isn’t the problem. Impact is the question. Is the access having any impact? So far I would say we haven’t done real well.”

He added, “We have a president who is on all sides and no side.”

On specific issues, Mr. Trumka criticized Mr. Trump for failing to “label China as a currency manipulator” and said the president had rejected plans to “revitalize our coal communities.”

“And despite calling himself a ‘builder president,’” Mr. Trumka continued, “he’s done nothing to invest in America’s infrastructure.”

“He promised a trillion and we’ve seen nothing so far,” Mr. Trumka said of the president’s pledge to deliver an enormous program to rebuild the nation’s crumbling roads, bridges and other infrastructure.

“He tells whoppers all the time and denies the obvious truth,” Mr. Trumka said.

Mr. Trumka said his union would participate aggressively in the midterm elections, backing candidates who supported its agenda in what he labeled “Tier 1” states like Pennsylvania, Ohio and Michigan, and in Florida, Illinois, Missouri, New Mexico and Arizona. Labor unions will also target another dozen states.

Historically, labor has aligned strongly with the Democratic Party, but Mr. Trump’s election showed that many in the rank and file were open to a Republican candidate. Mr. Trumka said union members were willing to vote for Mr. Trump because they felt establishment candidates in both parties had failed them, and they were ready to give the first-time politician “a chance.”