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GOP Sen. Thom Tillis on Wednesday strongly criticized Stephen Miller, going so far as to suggest that the senior White House adviser’s job should be at risk for his recent comments on US control of Greenland.

“See if Stephen Miller needs to get in a lane where he knows what he’s talking about or get out of this job,” Tillis told CNN’s Jake Tapper on “The Lead.”

The retired North Carolina senator’s comments are the strongest sign from a Republican lawmaker since the White House deputy chief of staff said the US has the right to take Greenland.

Tillis, who has served as the top Republican on the bipartisan Senate NATO oversight group since 2018, cautioned that Miller’s post has significant political implications.

Calling the NATO alliance “critically important,” he told Tapper that “it signals a shakeup of the alliance. [Russian President Vladimir] Putin has won.”

“And Stephen Miller doesn’t represent the U.S. government, he represents the Article II branch. And I, as a member of the U.S. Senate, want to weigh in on this issue,” he continued. “And I know, whether they say it out loud or not, most of my colleagues agree with me.”

When pressed about why more Republicans weren’t speaking out, Tillis said, “It’s pretty straightforward in this case. That’s my role as the Republican leader of the Senate NATO Observer Group.”

“It’s very important for the NATO alliance to know that we have their back because they’ve got ours.”

“We need to make it clear that our ability to project our power and our ability to stand up to Putin, to deter Russia, to keep China, Iran at bay, is all dependent on this great capability under NATO,” he said.

The comments came hours after Tillis gave a riveting speech on the Senate floor.

“I’m sick of stupid,” a fiery Tillis declared in the Senate. “I want good advice for this president, because I want this president to have a good legacy. And this nonsense about what’s happening in Greenland is a distraction from the good work he’s doing, and the amateurs who think it’s a good idea should lose their jobs.”

On Monday, Miller insisted in an interview with Tapper that the official position of the Trump administration is that “Greenland should be part of the United States.”

Miller also questioned Denmark’s claim to the Arctic region. “What is the basis for their territorial claim? What is the basis for having Greenland as a colony of Denmark?” He said.

Tillis told Topper that Miller’s CNN interview was “horribly executed” on “a subject he knew nothing about.”

“What I saw in your interview was unacceptable,” Tillis added, “and it drove me a little crazy.”

Earlier, he told his colleagues that Miller’s comments were “absurd.”

“Mr. Miller said that the US government – obviously Greenland should be part of the US. That’s absurd,” he said.

Tillis also warned that Miller’s comments detracted from the Trump administration’s military operations in Venezuela.

“What makes me mad? Stupid. What makes me mad when people don’t do their homework. When we tarnish the extraordinary execution of a mission in Venezuela that we fully support and make crazy comments about how Danish state-owned territory is our right.” Tillis said.

“Folks, amateur time is over. You don’t speak for this US senator or congressman,” he continued.

In his floor remarks, the North Carolina senator emphasized the value of the NATO alliance and Denmark’s role in it. He pointed out Denmark’s “disproportionately high” contribution to the NATO response after the September 11, 2001, terrorist attacks in the US, where they lost 43 soldiers out of a national population of 6 million in Afghanistan.

“You want me to thank the president for all the good things he’s done? Then give him good advice,” Tillis said.

Tillis previously issued a joint statement with Sen. Jeanne Shaheen, the top Democrat on the Senate NATO Observer Group and the Senate Foreign Relations Committee, criticizing the administration’s approach to Greenland.

“While Denmark and Greenland make clear that Greenland is not for sale, the United States must honor its treaty obligations and respect the sovereignty and territorial integrity of the State of Denmark,” the co-chairs said. “Any suggestion that our nation subjects a NATO ally to coercion or external pressure undermines the principle of self-determination that exists to protect our alliance.”

This story has been updated with additional developments.

CNN’s Kit Maher contributed to this report.

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