BEIJING (Reuters) - China is focused on solving the Korean Peninsula nuclear issue through talks and peaceful means, Chinese President Xi Jinping told U.S. President Donald Trump in a telephone call on Wednesday.

FILE PHOTO: U.S. President Donald Trump and Chinese President Xi Jinping (R) shake hands prior to a meeting on the sidelines of the G20 Summit in Hamburg, Germany, July 8, 2017. REUTERS/Saul Loeb/Pool/Files

The United States and South Korea have asked the United Nations to consider tough new sanctions on North Korea after its nuclear test on Sunday that Pyongyang said was an advanced hydrogen bomb.

Washington and its allies have said there is a growing urgency for China, North Korea’s top ally and trading partner, to apply more pressure on its already isolated neighbor to get it to back down on its nuclear weapons and missiles programs.

China’s focus on negotiations contrasts with Trump’s assertions over the last few days that now was not the time to focus on talks with North Korea.

In a telephone call with U.K. Prime Minister Theresa May on Tuesday, “President Trump reiterated that now is not the time to talk to North Korea, and made clear that all options remain open to defend the United States and its allies against North Korean aggression,” the White House said on Wednesday.

However, the issue was not mentioned in a separate White House statement on the Trump-Xi call, which said only that the two leaders recognized the danger posed by North Korea and committed to working together with the goal of denuclearizing the Korean Peninsula.

Earlier, a statement from China’s foreign ministry said China “unswervingly” works to realize denuclearization on the Korean Peninsula and to safeguard the international nuclear non-proliferation system, Xi told Trump.

“At the same time, we always persist in safeguarding peace and stability on the Korean Peninsula and resolving the issue through dialogue and consultation,” Xi said.

“It is necessary to stay on the path of a peaceful solution.”

Xi also said that China attaches importance to Trump’s visit to China later this year.

The statement cited Trump as saying that the United States was deeply concerned about the Korean nuclear issue and that it valued China’s “important role” in resolving the problem.

U.S. Ambassador to the United Nations Nikki Haley accused North Korean leader Kim Jong Un on Monday of “begging for war” and urged the Security Council to impose the “strongest possible” sanctions.

Beijing has said reining in North Korea is not chiefly its responsibility, and has expressed doubts that U.N. economic sanctions, which it has backed, will resolve the situation.

Sanctions so far appear to have done little to stop North Korea from boosting its nuclear and missile capacity as it faces off with Trump, who has vowed to stop Pyongyang from being able to hit the U.S. mainland with a nuclear weapon.

It is unclear if China will back further sanctions. Beijing fears that completely cutting off North Korea could lead to its collapse, unleashing a wave of refugees into China’s northeast.

China accounted for 92 percent of North Korea’s trade in 2016, according to South Korea. China’s foreign ministry said on Tuesday it would take part in Security Council discussions in “a responsible and constructive manner”.

China and Russia have advocated a plan in which the United States and Seoul stop major military drills in exchange for North Korea halting its weapons programs, but neither side is willing to budge.

Trump and Xi last spoke by telephone on Aug. 12. The White House said at the time that their relationship was “extremely close” and “will hopefully lead to a peaceful resolution of the North Korea problem.”

But tensions in China-U.S. ties have increased since Trump took office, with the U.S. president having authorized an investigation into China’s alleged theft of intellectual property, and suggesting trade relations would be linked to Beijing’s help on North Korea.