China has shown an increasing understanding of the importance of denuclearizing North Korea and the need to apply pressure on the regime in Pyongyang to realize the goal, a White House official said.

Ben Rhodes, deputy national security adviser for strategic communications, made the remark during a conference call Tuesday evening to preview an upcoming summit between President Barack Obama and Chinese President Xi Jinping.

"On Iran, China was instrumental in reaching the P5+1 agreement. On North Korea, I think we've seen in recent years an increasing Chinese willingness to understand that we need to be underscoring the necessity of denuclearization, and as necessary applying pressure on the North Korean regime," Rhodes said.

National Security Council Senior Director for Asian Affairs Daniel Kritenbrink also said during the call that he expects international security issues, such as Iran and North Korea, to be "a real focus" of the summit set for Friday.

The summit comes as tensions on the Korean Peninsula flared anew after the North strongly hinted it would conduct a banned long-range rocket launch, possibly around next month's ruling party anniversary. Pyongyang also said its bomb-making nuclear facilities have returned to normal operation and it could conduct a nuclear test if necessary.

On Monday, U.S. National Security Adviser Susan Rice said that the U.S. and China are "united in demanding the complete and verifiable denuclearization of the Korean Peninsula" and won't accept North Korea as a nuclear weapons state.

Calling China a "fulcrum of influence" for the North, Rice also said this week's summit will be an important opportunity to discuss "how we can sharpen Pyongyang's choices between having nuclear weapons and developing economically."

Xi also said China is firmly committed to a nuclear-free Korean Peninsula.

In an interview with the Wall Street Journal published Tuesday, Xi said that China's position for denuclearization of the Korean Peninsula is "firm and clear-cut" and that the country will work closely with the U.S. to realize the goal through peaceful means.

Xi began a weeklong state visit to the U.S. on Tuesday with a stop in San Francisco. It's his second visit to the U.S. since taking office in 2013.

China is North Korea's last remaining major ally and a key provider of food and fuel. But it has been reluctant to use its influence for fear that pushing the regime too hard could result in instability on the border and hurt Chinese national interests.

Analysts say that China has often increased pressure on the North, especially when Pyongyang defies international appeals and carries out nuclear tests and other provocative acts, but never went as far as to cause real pain to the North.

They also note that China's strategic calculus of North Korea is unlikely to change anytime soon, even though relations between Pyongyang and Beijing have significantly soured since North Korean leader Kim Jong-un rose to power. (Yonhap)