GREEN BAY, Wis. - Donald Trump endorsed Arizona Sen. John McCain Friday evening at a rally in Green Bay, the latest twist in a yearlong feud that started with Trump disrespecting McCain's military service.

"I hold in the highest esteem Sen. John McCain for his service to our country in uniform and in public office," Trump said in a monotone voice, reading from a prepared text. "I fully support and endorse his election. We will work together."

A McCain spokeswoman did not respond to a request for comment. McCain has not formally endorsed Trump. His stock response has been, "I support the nominee."

Bitter verbal battle this week

The Trump endorsement culminates a week in which both men traded insults. The fact that a Republican presidential nominee's endorsement of one of the leaders of his own party is news reflects the turmoil within the GOP.

This was the bitter back-and-forth this week leading up to the endorsement:

Monday: McCain slammed Trump for "defaming" the family of a Muslim-American soldier who was killed in Iraq.

Tuesday: Trump told the Washington Post: “I haven’t endorsed John McCain. I’ve never been there with John McCain because I’ve always felt that he should have done a much better job for the vets."

Wednesday: At a Phoenix news conference, McCain cut off all questions seeking his response to comments by Trump.

'He's not a war hero'

Their public feud began a year ago, after Trump said of McCain: “He’s not a war hero.”

“He was a war hero because he was captured," Trump said. "I like people who weren’t captured.”

McCain endured torture by his captors during more than five years as a prisoner of war in North Vietnam.

Trump's endorsement of McCain came as the celebrity billionaire struck a rare note of party unity at the Green Bay rally. Trump formally endorsed House Speaker Paul Ryan and New Hampshire Sen. Kelly Ayotte.

Trump has come under intense pressure from leading Republicans in the last few days to end his battles with leading GOP officeholders.

Awkward for both men

The McCain endorsement might prove awkward for both men. Trump supporters are drawn to him as the outsider who rejects GOP establishment types like McCain, a five-term senator.

McCain's base represents the part of the Republican Party that is appalled by Trump.

McCain's leading opponent in the August Senate primary, former state Sen. Kelli Ward of Lake Havasu City, had crowed earlier this week about having Trump's "unofficial" endorsement.

In a statement Friday evening, the Ward campaign said Trump "tepidly endorsed her opponent":

“Once he’s elected president, Donald Trump will need a strong partner in the U.S. Senate to Make America Great Again, and that partner is not John McCain, the ultimate establishment insider and Hillary’s favorite Republican, who has repeatedly trashed Trump and his supporters on issue after issue."