Senator John McCain has left little doubt that he was thinking of President Donald Trump when he criticised wealthy Americans who avoided military service during the Vietnam War.

Mr McCain, decorated former pilot and prisoner of war, stopped short of labelling Mr Trump a “draft dodger” for seeking five draft deferments that saw him sit out the Southeast Asian conflict.

But the senator’s comments came with Mr Trump already immersed in controversy over how he honours US troop deaths, and underscored the remove between the billionaire president and the military system he now controls as commander-in-chief.

Mr McCain’s criticism also continued a long-running stoush between the two fellow Republicans on the eve of a visit by Mr 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,” Mr McCain said on ABC’s The View.

WATCH: @SenJohnMcCain doesn't consider Trump a "draft dodger," but calls it "disgraceful" that system allowed wealthy to avoid service. pic.twitter.com/6M8dDVyNZY

— The View (@TheView) October 23, 2017

He was being pressed about comments in an earlier interview that aired on Sunday when 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 Mr Trump’s deferments came as a result of a doctor’s letter stating he suffered from bone spurs in his feet. His presidential campaign described the issue as a temporary problem.

While Mr McCain did not mention Mr Trump directly in the interview, his choice to use bone spurs as an example, when Americans received exemptions for manifold other conditions, was widely seen as a thinly veiled swipe at the President.

On The View, which is co-hosted by Mr McCain’s daughter Meghan, the senator did not deny that he had been referring to Mr Trump.

When one of the hosts said that people believed he was talking about Mr Trump because the President had sought a medical deferment, Mr McCain interjected saying: “More than once, yes”.

Mr McCain also made it clear he was critical of the President for his past comments about prisoners of war.

During the 2016 US presidential campaign, Mr Trump said Mr McCain was not a war hero because “I like people who weren’t captured”.

Mr McCain, 81, is battling brain cancer.

– With agencies