US President Donald Trump said Wednesday that it is “my responsibility” to address North Korea’s nuclear and missile threats, as he is set to start a summit with Chinese President Xi Jinping.

“We have a big problem,” Trump said during a joint news conference with Jordanian King Abdullah II at the White House, referring to North Korea and its leader Kim Jong-un.

“We have somebody that is not doing the right thing. And that’s going to be my responsibility. But I’ll tell you, that responsibility could have been made a lot easier if it was handled years ago.”

Trump has been ratcheting up pressure on China over North Korea’s nuclear and missile threats ahead of his first summit with Xi, which is scheduled to begin Thursday at his Mar-a-Lago resort in Florida.

With North Korea topping the agenda, their two-day gathering is to pose an early test of the two countries’ diplomacy. The two leaders will also face off over China’s escalating economic retaliation against South Korea over the ongoing deployment of the US’ Terminal High Altitude Area Defense anti-missile assets here, territorial disputes in the South China Sea, trade and other bilateral, regional and global issues.

Pyongyang has in recent months been carrying out a series of missile and engine tests, with satellite imagery pointing to signs of a fresh underground detonation. In the latest provocation, it fired a ballistic missile into the East Sea on Wednesday, though it appears to have failed.

While carrying out a North Korea policy review, Washington has displayed its willingness to sanction more Chinese companies dealing with North Korea, and raised the possibility for military action as one of its options.

Trump has indicated he will use trade as leverage to press Beijing to play a greater role in containing the Kim Jong-un regime’s nuclear and missile program. He also called North Korea a “humanity problem” Tuesday, and warned that the US is ready to tackle it on its own if China does not help, in an interview released Sunday.

In a phone call later in the day with Japanese Prime Minister Shinzo Abe, Trump also said that “all options are on the table” and called the North’s newest missile launch a “dangerous provocation and grave security threat,” Abe told reporters.

Matt Pottinger, senior director for Asia at the National Security Council, called the secondary sanctions a “very much live” question for the summit, saying China has the ability to squeeze the North “in a way that no other single country can.”

“We’d like to see China working closely with the US to address the menace emanating from North Korea, their weapons programs, the provocations that we’ve seen every week, missile launches, including one that we had not too many hours ago,” he said at a separate news conference Wednesday for foreign press.

“I think that North Korea long ago ceased to be a strategic asset for China. It is now quite clearly a strategic liability and it is one that is having an impact on the region. It is one that has the potential to destabilize not only the peninsula, but really the region as well.”

Seoul, for its part, has been intensifying diplomatic efforts to raise its voice on North Korea and China’s THAAD retaliation.

Seoul’s National Security Office chief Kim Kwan-jin and US National Security Adviser H.R. McMaster held a phone conversation early Thursday, condemning Pyongyang’s ongoing missile liftoffs and reaffirming the THAAD stationing plan, Cheong Wa Dae said.

Kim Hong-kyun, special representative for Korean Peninsula peace and security affairs at the Foreign Ministry here, also had separate phone calls with the top nuclear negotiators of the US and Japan -- Joseph Yun and Kenji Kanasugi -- to review the newest missile test and coordinate responses to Pyongyang’s additional provocations, the ministry said.

Following the Trump-Xi meetings, Washington would seek a top-level consultation to brief Seoul on its results and facilitate joint next steps, a ministry official told reporters on the customary condition of anonymity.

“We expect the forthcoming US-China summit will provide a critical chance in the international community’s efforts to resolve the North Korean nuclear issue,” ministry spokesperson Cho June-hyuck said at a regular news briefing, noting Pottinger’s portrayal of Pyongyang as Beijing’s strategic liability.

“South Korea and the US share a solid view that China’s role is more important than anything else in leading North Korea to the path of denuclearization.”

By Shin Hyon-hee (heeshin@heraldcorp.com)