Trump: If China wants to solve ‘North Korean problem,’ they will

President TrumpDonald John TrumpMichelle Wolf in July Fourth salute: 'God bless abortions and God bless America' Graham: Trump's Supreme Court picks 'all winners' Man arrested after allegedly threatening to kill Trump supporters, GOP lawmaker MORE on Friday put new pressure on China to rein in North Korea, saying "if they want to solve the North Korea problem, they will."

"China is very much the economic lifeline to North Korea so, while nothing is easy, if they want to solve the North Korean problem, they will," Trump tweeted.

China is very much the economic lifeline to North Korea so, while nothing is easy, if they want to solve the North Korean problem, they will

— Donald J. Trump (@realDonaldTrump) April 21, 2017

On the campaign trail, Trump vowed to pressure China to crack down on North Korea for its nuclear and missile programs. But Trump appeared to change his tone on the matter last week after meeting with Chinese President Xi Jinping.

During the meeting, Trump told The Wall Street Journal, he "realized it's not so easy" after Xi explained the relationship between China and North Korea. China is North Korea's sole major ally.

Trump's comments on Friday come amid heightened tensions between the U.S. and North Korea, with both sides floating the possibility of military action against one another.