NEW YORK (CBSNewYork/AP) — President-elect Donald Trump is lashing out at CIA chief John Brennan for saying the president-elect doesn’t understand the threat posed by Russia.

Trump tweeted of Brennan, “Was this the leaker of Fake News?”

The Sunday night jab was a reference to a recent intelligence briefing that raised questions about Trump’s connections to Russian President Vladimir Putin.

The CIA director said Sunday morning on Fox News that Trump lacks “full appreciation and understanding” of the implications of lifting sanctions on Russia.

“I don’t think he has a full appreciation of Russian capabilities, Russia’s intentions and actions that they are undertaking in many parts of the world. And that’s what the obligation and responsibility of the intelligence community is,” Brennan said. “I very much hope that our relationship with Russia improves in the incoming administration.”

Trump acknowledged Brennan’s criticism and said he “couldn’t do much worse” as president.

Meanwhile preparations are in full gear and emotions are already running high in the days ahead of inauguration day.

At a parade practice run on Sunday, stand-ins tried to make it look like the real deal, with security in place, CBS2’s Jessica Moore reported.

PHOTOS: Trump Inauguration Rehearsal In Washington D.C.

Temporary fences are up around much of the city, and Homeland Security Secretary Jeh Johnson says law enforcement is ready.

“This includes approximately 10,000 individuals from the Department of Homeland Security, plus 12,000 other federal personnel – including approximately 7,800 members of the National Guard,” Johnson said.

On “Face The Nation” Sunday, Vice President-elect Mike Pence defended the legitimacy of the incoming Commander-in-Chief.

“Donald Trump won by a landslide,” Pence said. “The American people spoke decisively.”

A growing list of more than a dozen House Democrats are refusing to attend Trump’s inauguration, including civil rights icon Rep. John Lewis. Trump slammed Lewis on Twitter Saturday, after the congressman questioned the President-elect’s legitimacy as a leader.

The tweets angered Democrats, some in the black community and others in Lewis’ district.

Brooklyn congresswoman Yvette Clark told WCBS 880’s Mike Smeltz her decision to sit out the inauguration has been growing as she’s learned more about Russia’s influence on the election.

“With all due resepct, this is highly unusual, and I don’t want to contribute to normalizing it,” Clark said.

Clark, a Democrat, said Trump’s tweets about Lewis out an exclaimation point at the end of her decision to boycott.

Republican congressman Peter King, of Long Island, said Inauguration Day is a celebration of democracy and should be above partisanship.

“I think it sends a very bad signal to the world, a bad signal to the country and it only encourages dis-unity,” King said.

Pence said he was deeply disappointed by Lewis’ comments, and predicted better ties with Russia.

“In the President-elect you have someone who is willing to approach this terrible relationship the United States has with Russia today with fresh eyes, and to at least be open to a better relationship with Vladimir Putin and with Russia,” Pence said.

Music stars Toby Keith, 3 Doors Down and Lee Greenwood will headline the inaugural concert Thursday night. Broadway star Jennifer Holliday backed out over the weekend because of backlash from the LGBT community.

CBS2 will have complete coverage of the inauguration starting Thursday night.

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