North Korea's leader Kim Jong Un has planned a "provocative act" that will test the strength of U.S.-China relations, a U.S. lawmaker told South Korea's Yonhap News Agency on Tuesday.

The news comes amid growing tensions between North Korea and the U.S. while President Donald Trump continues to vow to take strong actions to combat Pyongyang's nuclear threat.

"The next step is going to be forced on the president because the next step will be a provocative act by North Korea that will force the president to confront China on its North Korea policy," said Rep. Adam Schiff (D-CA), the top Democrat on the House Intelligence Committee, at a breakfast hosted by the Wall Street Journal. "I think that will happen before we have any intensive trade discussions."

North Korea has continued its advancement of nuclear capabilities despite sanctions from the United Nations, raising concerns that Pyongyang could soon perfect the capability to miniaturize a nuclear warhead and mount it on an intercontinental ballistic missile while Trump is in office, Schiff said.

"The key here is China, and where we do see China cracking down?" Schiff was quoted as saying. "We see it has a big impact on North Korea and periodically they are willing to crack down."

Relations between the U.S. and China have been strained since Trump took office as the real estate mogul condemned Beijing multiple times for not doing enough to foil Pyongyang’s nuclear and missile efforts.

Earlier this year, when North Korea declared its plans to test an intercontinental ballistic missile, Trump tweeted: "China has been taking out massive amounts of money & wealth from the U.S. in totally one-sided trade, but won't help with North Korea. Nice!"

Schiff reportedly said that China would be willing to put more pressure on the North if the "costs of inaction on their part are too high."

Early January, China expressed concern over North Korea’s repeated threats to test-launch an intercontinental ballistic missile.

“We are seriously concerned over this… We call on all sides to refrain from actions that could escalate the situation. We will closely monitor the situation and try to contribute to upholding peace and stability on the peninsula,” Chinese foreign ministry spokesman Lu Kang said at the time. “The United Nations Security Council has clear rules for North Korea regarding its use of ICBM technology to test missiles. In this complex and sensitive situation, China asks all relevant parties to not engage in acts that will raise tensions."

During the New Year's Day address, Kim announced that the country has entered the final stage of preparations to test-fire an ICBM capable of carrying a nuclear warhead.