Sen. Mazie HironoMazie Keiko HironoConservative justices signal willingness to uphold travel ban Former Sen. Daniel Akaka of Hawaii dies at 93 Dems to top DOJ officials: Publicly promise not to interfere in Mueller's probe MORE (D-Hawaii) argued Tuesday that President Trump's attacks on Sen. John McCainJohn Sidney McCainSenate panel advances 6B defense policy bill McCain: Trump pardoning Jack Johnson 'closes a shameful chapter in our nation’s history' Trump pardons late boxing champion Jack Johnson MORE (R-Ariz.) show the president to be "egocentric."

In an interview on CNN, the Hawaii Democrat said Trump should focus on more important issues, rather than personal attacks aimed at lawmakers.

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"It just goes to show how egocentric the president is," Hirono said. "Frankly, the way I look at it, there are a lot of problems and concerns that he should be addressing."

Hirono pointed to rising health-care premiums in her home state as an immediate concern that she claimed Trump is ignoring.

"He has said ObamaCare is dead, which means that the president owns health care in our country now, and because he has ended the subsidies, health-care costs will go up immediately," she said, referring to the administration's move last week to stop key payments to insurers.

"I know for a fact that in Hawaii, everyone in Hawaii will see their health-care costs go up by 5 to 8 percent because of the stopping of the subsidies," she continued.

"So those are the things that he should be concerned about, and I'm sorry that he's attacking a true war hero, something he doesn't seem to really understand or appreciate."

Hirono's remarks come hours after Trump threatened to "fight back" after McCain's denunciation of nationalist politics that many saw as a thinly-veiled shot at the Trump administration.

"People have to careful, because at some point I fight back," Trump told WMAL radio host Chris Plante on Tuesday. "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 responded to Trump's comments moments later, saying that he has "faced far greater challenges than this," according to CNN.