House Intelligence Committee Chairman Adam Schiff vowed on Sunday to continue the investigation into President Trump's finances and foreign connections for as long as it takes.

Speaking during an interview on NBC’s “Meet The Press,” the California Democrat said he found it “remarkable” that Trump was seeking a business deal with Russia and that he wanted to make sure that the president was “working in the national interest.”

“We are looking to see if the president is working in the national interest,” Schiff said. “That he is not motivated by some pecuniary interest or fear of compromise or actual compromise.”

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Schiff last week hired former National Security Council staffers to work for him as he launches a sweeping new investigation into Trump – a move that appears to have drawn particular ire from the president.

Trump tweeted Thursday that Schiff and Democrats were going "nuts" with investigations and wrote, without elaborating, that they were "even stealing people from the White House!"

It's unclear exactly who Trump was talking about, but the tweet comes as Schiff appears to have hired at least one staff member who served on the National Security Council under Trump. The staff member, Abigail Grace, is listed in a House directory as working for Schiff on the intelligence panel. A person familiar with the committee's staff confirms that she is working for the panel and used to work for the NSC.

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Grace worked for a bipartisan think tank, Center for a New American Security, after working for both former President Barack Obama and Trump on the National Security Council from 2016 to 2018. She focused on Asia-Pacific security issues, according to a spokesman for the group.

Schiff wouldn't confirm the hires in an interview Thursday, but hinted at them while snapping back at Trump.

"We have a long tradition of hiring out of the intelligence community, out of the National Security Council, and if the president is worried about our hiring any former administration people maybe he should work on being a better employer," Schiff said.

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A committee aide said that none of Schiff's staff have come directly from the White House, but said the panel has hired people with prior experience on the National Security Council staff.

"We do not discriminate against potential hires on the basis of their prior work experience, including the administration," the aide said. The person also declined to be identified because they were not authorized to speak publicly about confidential committee business.

The Associated Press contributed to this report.