Donald Trump doubled down Sunday on hard-line campaign pledges to impose trade tariffs and carry out mass deportations, while dangling the idea that the United States could withdraw from NATO.

In his first formal television interview -- and just six weeks before he takes office -- Trump again signaled that US support for Ukraine will scale back, saying he will "probably" cut the aid helping Kyiv repel the Russian invasion.

Trump also said he would "very quickly" look at pardons for supporters jailed for storming the US Capitol after his 2020 election defeat to Joe Biden.

The interview on NBC's "Meet the Press with Kristen Welker" was taped Friday but aired Sunday, following Trump's meetings with the presidents of France and Ukraine over the weekend -- his first foreign trip since winning the November election against Biden.

Trump reiterated his familiar threat to leave NATO, the cornerstone of security in Europe since World War II, saying that US allies do not pay enough for their defense.

"If they're paying their bills, and if I think they're treating us fairly, the answer is absolutely I'd stay with NATO," said.

But there is also "absolutely" the possibility of America's departure, he said.

He also stressed that his campaign promises of huge tariffs -- including against top US trading partners Canada, Mexico and China -- would be enacted.

"We're subsidizing Mexico and we're subsidizing Canada and we're subsidizing many countries all over the world," he said.

Vowing that "properly used" tariffs are "a very powerful tool," Trump added that he would not only wield them economically, "but also for getting other things outside of economics."

As to whether Americans would see higher prices as a result of those tariffs, Trump said that "I can't guarantee anything. I can't guarantee tomorrow."

- Domestic pledges -

Trump has a history of breaking with precedent to undermine the independence of the US Federal Reserve, but he promised not to replace Chairman Jerome Powell.

However, Trump said he would go ahead with what economists say could be the hugely disruptive mass deportation of undocumented immigrants in the United States.

"I think you have to do it, and it's a hard -- it's a very tough thing to do. But you have to have rules, regulations, laws. They came in illegally," he said.

He said he would end the constitutionally protected right to US citizenship for anyone born in the country, calling it "ridiculous." It is unclear how Trump would be able to do this but he suggested, "if we can, through executive action."

"We're going to have to get it changed. We'll maybe have to go back to the people. But we have to end it," Trump said.