The first face-to-face meeting between US President Donald Trump and President Xi Jinping ( 習近平 ), at Trump’s private estate in Florida, was designed as an informal, get-to-know-you, kind of diplomacy. But the relationship-building exercise wrapped up on a surprisingly upbeat note, as Trump talked of “the tremendous goodwill and friendship” between the leaders of the world’s two largest economies and most influential nations, while Xi suggested “ a thousand reasons to get China-US relations right , and not one reason to spoil the China-US relationship”. Watch: Trump says he has developed a friendship with Xi However, the real test of such rapport came no sooner than Xi had left the US, as the possibility emerged of US military action against North Korea – which counts China as its main ally – with Trump ordering a strike group led by the nuclear-powered aircraft carrier USS Carl Vinson to sail into the western Pacific. This possibility gained traction following US missile strikes against Syria last week, even as Trump and Xi sat down for a formal dinner . It was further fuelled by overwhelming fears that North Korea is close to acquiring the capacity to launch nuclear warheads as far as the US west coast. Pyongyang celebrates several major anniversaries this month, and it often marks the occasions with major tests of military hardware. The summit at the US president’s Mar-a-Lago estate apparently failed to reach concrete agreement on the North Korea issue, as Trump told Xi that Washington is “prepared to chart their own course”. Some analysts viewed the timing of the US strike on Syria as no coincidence, seeing it as a prod to China to do more to dismantle Kim Jong-un’s nuclear programme, or a blunt message to Xi that the US might act soon, even without more robust Chinese help. North Korea is looking for trouble. If China decides to help, that would be great. If not, we will solve the problem without them! U.S.A. — Donald J. Trump (@realDonaldTrump) April 11, 2017 <!--//--><![CDATA[// ><!-- //--><!]]> China has opposed all US military operations overseas, including those in the Middle East, such as its intervention in Libya in 2011 and the Iraq invasion in 2003. The US strike on the Shayrat air base in central Syria also lent credibility to Washington’s other warnings to China, that it would take a tough stance on the Chinese military’s assertive activities, whether in the South and East China seas or Taiwan. There is no room for China to maintain a bystander-like neutral stance, as the war would be on its doorstep However, both Washington and Beijing understand that the situation on the Korean peninsula is more complicated than that in Middle East. If the US starts a war against North Korea , it should be well prepared for Pyongyang’s military retaliation against South Korea, Japan and US armies stationed in both countries. Given the North’s sensitive geopolitical status and its possession of nuclear weapons, a war would destabilise the region and potentially cost millions of lives. Therefore, there is no room for China to maintain a bystander-like neutral stance, as the war would be on its doorstep. North Korean ships return home with coal after China tightens sanctions As China is North Korea’s sole supporter and major economic benefactor – its main source of arms, food and energy – Beijing has the most leverage over the erratic and isolated dynastic regime . For all his sabre-rattling and coercive diplomacy, Trump apparently needs Xi’s help to fend off a crisis sure to inflict pain on all involved. I explained to the President of China that a trade deal with the U.S. will be far better for them if they solve the North Korean problem! — Donald J. Trump (@realDonaldTrump) April 11, 2017 <!--//--><![CDATA[// ><!-- //--><!]]> In this regard, the Florida summit helped push Beijing to adopt a new diplomatic focus and urgency in dealings with Pyongyang . It also proved what Xi has said: that there are “a thousand reasons” to cooperate and not “one reason” to bedevil the most significant bilateral relationship in global diplomacy. For sure, both Beijing and Washington have the political will to work to maintain such momentum, as the Chinese prepare for Trump’s return visit later this year. Cary Huang is a senior writer at the Post