"It may take longer than I'd like. It may take longer that you'd like," he said. "But there will be success in the end one way or the other."

Trump also told Xi that trade is a "very, very big issue for the United States.

Trump has increasingly expressed frustration after months of fruitless efforts to persuade Beijing to exercise more of its influence as the North's economic lifeline to rein in the regime.

China accounts for nearly 90 percent of the North's total trade.

Trump's frustration appears to have deepened after the North's first ICBM test Tuesday.

On Wednesday, Trump questioned the sincerity of China's efforts to pressure the North. He pointed out that trade between China and the North has grown nearly 40 percent, leading him to say, "So much for China working with us."

Trump first complained about China last month, saying Chinese efforts have "not worked out."

Since then, the US has downgraded China's human trafficking status, blacklisted China's Bank of Dandong as a primary money laundering concern and approved the first arms sales to Taiwan since Trump came into office.

These contrasted sharply with April's decision not to label China a currency manipulator in order to avoid hurting Chinese feelings at a time when the US was asking for its help to bring the provocative regime in Pyongyang under control.

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

Analysts doubt how far China can go in pressuring Pyongyang, saying China has often increased pressure on the North in the past, especially when Pyongyang carried out nuclear and missile tests and other provocative acts, but it never went as far as to cause real pain.

Earlier, Trump also met one-on-one with Japanese Prime Minister Shinzo Abe.

"We made a lot of progress on trade and other elements. We're also talking, obviously, about North Korea, and the problem and menace of North Korea," Trump said. "The prime minister is -- I will say this -- very, very focused on what's going on with respect to North Korea. So we will continue those discussions."

Abe said that the security environment in the Asia-Pacific region, including North Korea, has become "increasingly severe,"

and he wants to demonstrate the robust partnership and the bond between the two countries. (Yonhap)