WASHINGTON/BEIJING (Reuters) - The senior U.S. defense official for Asia said on Tuesday the United States wants China to improve its enforcement of sanctions on North Korea and take other steps to press Pyongyang to be more constructive in talks with the United States.

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Randall Schriver, the U.S. assistant secretary of defense for Indo-Pacific Security Affairs, told a Washington conference there had been some slippage in sanctions enforcement by China, particularly when it came to controlling ship-to-ship transfers of banned goods in its waters.

“We want them to do better,” Schriver said.

“At a minimum, sanctions enforcement, but I think there are other ways China could help pressure Pyongyang into being a more constructive participant in the talks, should they resume, and we are just not seeing this right now.”

Schriver, who spoke at an event organized by the Jamestown Foundation, was referring to efforts by the United States to revive talks aimed at persuading North Korea to give up its nuclear weapons.

Responding to Schriver’s comments, China’s foreign ministry said on Wednesday it has always fulfilled its duty pertaining to resolutions on North Korea from the U.N Security Council.

“China has been persistent in earnestly carrying out its duty in the resolutions related to North Korea. The concerned countries should all also completely carry out (the Security Council’s) aforementioned resolutions,” said Geng Shuang, a spokesman for the Foreign Ministry, at a daily press briefing.

“The Korean Peninsula’s denuclearization discussion is at a critical moment. We hope that all the concerned sides will continue to uphold the hard-earned ease in tensions and momentum in dialogue, (and) equitably push for progress in a political solution,” he said.

Earlier this month, the United States and North Korea held their first working-level talks since a failed summit in February between President Donald Trump and North Korean leader Kim Jong Un, but the North Koreans accused the U.S. side of inflexibility and have yet to say if they will attend another round.

China is North Korea’s neighbor and main ally. It is a signatory to tough U.N. sanctions on Pyongyang over its past nuclear and missile testing, but has urged the United States to adopt an approach more conducive to dialogue and suggested that sanctions relief be considered.