China and South Korea have agreed to impose “strong” new sanctions on North Korea if it carries out further nuclear or long-range missile tests, a senior official in Seoul said on Monday.

The commitment comes as pressure on Pyongyang mounts after last week’s summit between US President Donald Trump and President Xi Jinping.

Monday’s meeting in Seoul between China’s Special Representative for Korean Peninsula Affairs Wu Dawei and his South Korean counterpart Kim Hong-kyun also came as a US naval strike group led by the aircraft carrier USS Carl Vinson headed to the region in a show of force.

“In the midst of the growing possibility of North Korean provocations, The latest visit by Wu ­Dawei to Korea is very timely in terms of sending a strong warning to North Korea,” Yonhap news agency quoted Kim as saying.

Wu’s trip was the first to South Korea by a senior Chinese official since a diplomatic row erupted between Beijing and Seoul over South Korea’s planned deployment of the US’ Terminal High ­Altitude Area Defence system.

Analysts said Beijing appeared to be taking a more active role in warning North Korea not to test Beijing’s bottom line with more strategic military tests.

North Korea has several major anniversaries this month, including the 105th anniversary on Saturday of its founding leader’s birth, and often marks the occasions with major tests of military hardware.

The possibility of US military action against North Korea in response to such tests gained traction after last week’s strikes against Syria. But, Kim said, there was no mention of any military option in his talks with Wu. The two also did not discuss any possible strike against the North by the United States, he said.

“Both sides agreed that despite the international community’s warnings, if North Korea makes strategic provocations such as a nuclear test or an ICBM launch, there should be strong additional measures in accordance with UN Security Council resolutions,” Kim said.

Kim added the two sides agreed that “an even stronger UN resolution” would have to be adopted in the event of additional weapons tests by North Korea.

Wu did not speak to reporters.

Chinese chief nuclear envoy Wu Dawei is greeted by his South Korean counterpart Hwang Joon-kook during a meeting at the Ministry of Foreign Affairs in Seoul, South Korea, Sunday, Feb. 28, 2016. REUTERS/Ahn Young-joon/Pool Kim said Wu repeated China’s position on the THAAD system deployment, but did not give details. China has previously said the system would destabilise the regional security balance and that its radar’s reach would intrude into Chinese territory.

Meanwhile, Japanese Foreign Minister Fumio Kishida and US Secretary of State Rex Tillerson agreed yesterday on the sidelines of G7 meeting in Viareggio, Italy, to urge China to “play a bigger role” in halting North Korea’s nuclear and missile programmes.

in an interview broadcast on Sunday, Tillerson told CBS’s Face the Nation that when Trump and Xi met at the Mar-a-Lago resort last week, they “had extensive discussions around the dangerous situation in North Korea”.

US National Security Adviser HR McMaster also criticised North Korea as a rogue nation engaged in provocative behaviour and said denuclearisation of the peninsula “must happen”.

“The president has asked them to be prepared to give us a full range of options to remove that threat,” he said on Fox News, apparently referring to Trump’s advisers.

Wang Sheng, from Jilin University, said Beijing was sounding another alarm to Pyongyang, its long-time ally.

“It looks like China is trying to take a more proactive role to warn North Korea not to try to cross China’s bottom line,” Wang said, adding that China could impose tougher sanctions over food or even oil if Pyongyang continued to be provocative.

Lee Kyu-tae, a geopolitical analyst at South Korea’s Catholic Kwandong University, said Wu’s trip to Seoul might also help repair ties strained by the THAAD dispute.

“China has pressured South Korea over the THAAD deployment for months. It may need [to send someone] to South Korea to assess how to repair its relations with Seoul,” Lee said.

Zhang Tuosheng, from the China Foundation for International and Strategic Studies, agreed that Wu’s trip also serves to assess the latest development on deployment of the US anti-missile system.

“It is meaningful for Wu ... to reach out South Korean officials, prepare responses for further situations [on the peninsula], and also understand the developments over [THAAD],” Zhang said.