GOP vice-presidential nominee Mike Pence is greeted by House Speaker Paul D. Ryan before he addresses the Republican National Convention on July 20. (Michael Robinson-Chavez/The Washington Post)

As Donald Trump holds off endorsing House Speaker Paul D. Ryan in Wisconsin's Republican primary, his running mate enthusiastically endorsed Ryan on Wednesday, calling him a “longtime friend” and “strong conservative leader.”

“I strongly support Paul Ryan, strongly endorse his reelection,” Indiana Gov. Mike Pence said during an interview on Fox News on Wednesday afternoon. “I believe we need Paul Ryan in leadership in the Congress of the United States to rebuild our military, to strengthen our economy and to ensure that we have the kind of leadership in this country that will make America great again.”

Trump has angered his party's leadership by refusing to endorse Ryan or Sen. John McCain (R-Ariz.) in their primary campaigns. Both Ryan and McCain have endorsed Trump but have remained critical of many of his comments, including Trump's ongoing public feud with the parents of a Muslim American soldier killed in 2004. Wisconsin holds its primary Tuesday and the Arizona primary is later this month.  In an interview with The Washington Post on Tuesday, Trump praised Ryan’s underdog opponent, Paul Nehlen.

The Washington Post's Philip Rucker explains how unusual it is that Republican presidential nominee Donald Trump is withholding his endorsements of House Speaker Paul D. Ryan and Sen. John McCain (R-Ariz.) in their primary races. (Bastien Inzaurralde/The Washington Post)

“I like Paul, but these are horrible times for our country," Trump said in the interview. "We need very strong leadership. We need very, very strong leadership. And I’m just not quite there yet. I’m not quite there yet.”

Pence said that he discussed his endorsement of Ryan with Trump on Wednesday morning.

"He strongly encouraged me to endorse Paul Ryan in next Tuesday’s primary," Pence said, "and I’m pleased to do it."