(CNN) Maine's Republican Sen. Susan Collins criticized President Donald Trump for "alienating our closest allies" at the G7 summit, which she referred to as "an unfortunate incident."

"The President and his staff should not be alienating our closest allies, our longtime friends, our reliable allies and our biggest trading partners, in the case of the Canadians," Collins said on CNN's "Cuomo Prime Time" Tuesday evening.

Collins suggested that Trump's focus on his then-impending North Korea summit could have contributed to his actions at the G7 gathering.

"I think the President was not focused on the G7 meeting, that his mind was on the summit to come with North Korea," Collins told Chris Cuomo, "and I think that's very unfortunate because those allies are important."

Collins went on to call Trump's proposal to reinstate Russia to the G7 "a terrible idea." Russia was suspended from the group -- then known as the G8 -- in 2014 after the majority of member countries condemned Moscow's annexation of Crimea, which Russia continues to hold.

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