Stung by Senator John McCain’s condemnation of “spurious nationalism”, Donald Trump is looking for another fight with the former Presidential candidate and Vietnam War veteran.

Trump has repeatedly insulted McCain in the past, deriding the Arizona Senator’s 5 1/2-year captivity in North Vietnam, “I like people who aren’t captured”. His bitterness surged this summer when the senator cast a deciding vote to block the GOP’s repeal and replacement of ObamaCare.

On Monday night, McCain accepted the National Constitution Center’s Liberty Medal with a denunciation of “half-baked, spurious nationalism cooked up by people who would rather find scapegoats than solve problems”: “[It] is as unpatriotic as an attachment to any other tired dogma of the past that Americans consigned to the ash heap of history.”

McCain denied that he was specifically looking at Trump, “I was referring to the whole atmosphere and environment. No, there’s a whole lot of people besides the President who have said ‘America First.'”

But Trump was still angered, telling a radio host:

Well it’s a shocker. Yeah, well I hear it and people have to be careful because at some point I fight back. You know, I’m being very nice. I’m being very, very nice. But at some point I fight back and it won’t be pretty.

McCain, who is battling brain cancer, brushed off the warning, “It’s fine with me. I’ve faced some fairly significant adversaries in the past.”