Republican Sen. John McCain left no doubt Monday that he was thinking of President Donald Trump as he criticized the draft system during Vietnam for forcing low-income Americans to serve while the wealthy could avoid war with a doctor’s note.

McCain, a former Navy pilot and prisoner of war, stopped short of labeling Trump a “draft dodger” for getting five draft deferments. But the senator’s comments came with Trump already immersed in controversy over how he honors U.S. troop deaths, and underscored the remove between the billionaire president and the military system he now controls as commander in chief.

McCain’s criticism also continued a long-running clash between the two men on the eve of a visit by Trump to Capitol Hill on Tuesday to court Senate GOP votes for his tax plan, a meeting that could contain more than a few awkward moments.

“I don’t consider him so much a draft dodger as I feel that the system was so wrong that certain Americans could evade their responsibilities to serve the country,” McCain said on ABC’s “The View.” He was being pressed about comments in a C-SPAN interview aired Sunday where he lamented that the military “drafted the lowest income level of America and the highest income level found a doctor that would say they had a bone spur.”

One of Trump’s deferments came as a result of a physician’s letter stating he suffered from bone spurs in his feet. Trump’s presidential campaign described the issue as a temporary problem.

McCain, meanwhile, spent 5? years as a prisoner of war after his plane was shot down over North Vietnam in 1967. Yet during last year’s presidential campaign Trump said McCain was not a war hero because “I like people who weren’t captured.”

The senator made clear during Monday’s interview that he had been referring to Trump in making his C-SPAN comments. When one of the hosts remarked that people thought he was talking about Trump because the president had sought a medical deferment, McCain interjected, “More than once, yes.”

McCain was asked to describe his relationship with the president. “Almost none” he simply said.

The six-term Arizona lawmaker, battling brain cancer at age 81, made his appearance on “The View” in honor of his daughter Meghan McCain’s birthday. She recently joined the daytime talk show as one of its panel of co-hosts. The White House declined to comment on McCain’s remarks.

The tacit criticism reflected the ongoing tension between Trump and McCain, which began during last year’s campaign and has flared on and off. Trump responded furiously when McCain’s “no” vote sunk Senate efforts to repeal and replace “Obamacare” earlier this year.

And last week, in a speech in Philadelphia, McCain questioned “half-baked, spurious nationalism” in America’s foreign policy. Trump lashed out, insisting he would fight back and “it won’t be pretty.”

That prompted McCain to retort: “I have faced tougher adversaries.”

The senator burst into sustained laughter on Monday when one of the hosts mentioned Trump’s threats and asked McCain, “Are you scared?”

After he stopped laughing, McCain said, “I mentioned that I had faced greater challenges.”

“Let’s stop insulting each other. Let’s start respecting each other,” McCain recommended.

The back-and-forth between the president and McCain stands as the latest skirmish between the two Republican Party heavyweights and another example of Trump tangling with GOP senators who could make or break his agenda in Congress.

Trump in recent weeks has feuded with Tennessee Sen. Bob Corker and Senate Majority Leader Mitch McConnell, although the president joined with the Kentucky senator at the White House last week to publicly declare they were on the same page. Both Corker and McCain could be critical to the success or failure of the president’s push to overhaul the tax system.

During Trump’s presidency, McCain has questioned the president’s immigration policies and warned him against cozying up to Russian President Vladimir Putin. The senator also criticized Trump in August for saying that both white nationalists and counter protesters were responsible for violent clashes in Charlottesville, Virginia.

McCain insisted in a tweet at the time that “there’s no moral equivalency between racists & Americans standing up to defy hate and bigotry” and the president should say so.

The senator underwent surgery in mid-July to remove a 2-inch (51-millimeter) blood clot in his brain after being diagnosed with an aggressive tumor called a glioblastoma. It’s the same type of tumor that killed Sen. Edward M. Kennedy at age 77 in 2009 and Beau Biden, son of then-Vice President Joe Biden, at 46 in 2015.

(AP)