Like other such talks, the first summit meeting between President Moon Jae-in and US President Donald Trump had both ups and downs.

The biggest upside is that, dispelling presummit worries, the two leaders reaffirmed the security alliance between their two countries and agreed to work together to end North Korea’s nuclear and missile threats, which Moon called “the world‘s most urgent and most dangerous threat.”

Their agreement was summed up in a joint statement they issued after their talks in Washington: “They affirmed their commitment to fully implement existing sanctions and impose new measures designed to apply maximum pressure on North Korea to compel Pyongyang to cease its provocative actions and return to sincere and constructive talks.”

In short, the two leaders agreed to push both sanctions and dialogue. The agreement made it clear that dialogue with the communist state -- which obviously Moon prefers -- should proceed “under the right circumstances,” but it generally endorsed Moon’s efforts to improve inter-Korean relations within the bounds of the UN and US-led international sanctions on the North.

The agreement is welcome given there had been signs of differences in the allies’ approaches toward North Korea and its nuclear and missile provocations.

The two leaders prudently avoided directly discussing South Korea’s decision to delay deployment of a US missile shield system to counter North Korean missiles. Instead, Moon used a forum and a meeting with US Congress leaders to convince the US that he will not reverse the decision to deploy the Terminal High Altitude Area Defense system.

It was also well advised for Moon to reject the possibility -- previously raised by his top security adviser -- of scaling down the South Korea-US joint military exercises and reduce the presence of US strategic assets on the peninsula.

Another good point of the Moon-Trump agreement was that they did not expose any friction -- at least publicly -- over how to achieve denuclearization of North Korea peacefully.

As tensions escalated over the North’s continuing missile provocations, talk of a unilateral action by the Trump administration --including a pre-emptive strike against key North Korean facilities -- raised fear of the US bypassing South Korea.

Moon also secured Trump’s support for South Korea’s leading role in fostering an environment for peaceful unification of the Korean Peninsula and the work to “expeditiously” enable the conditions-based transfer of wartime operational control of South Korean forces.

All these may well strengthen the domestic political position of Moon, who restored the first liberal government in nearly 10 years with a pledge to be different from the two successive conservative governments over dealings with both the US and North Korea.

On his part, Trump did not forget his own domestic political considerations -- that is his pursuit of his “America First” policy -- in which he targeted the cost of stationing US forces in South Korea and the Korea-US free trade agreement.Trump made it clear that he wants to renegotiate the six-year-old FTA by saying that the two sides were renegotiating the deal and the new deal should be a “fair and equitable” one.

Trump also reiterated his demand for a “fair” sharing of the cost of American military presence in the South, which was one of his election pledges.

These battle cries demonstrate that Trump will not spare even the Korea-US alliance from his relentless pursuit of putting selfish American interests first.

Moon said that hopes to move the Korea-US alliance from a good one to a “great” one in the face of the North Korean threats.

One of the first steps Moon needs to work on for making the alliance a great one is to shake off domestic opposition and accelerate the deployment of the US missile shield system at an early date. On his part, Trump should not push his America First approach excessively, which could dent the alliance and South Koreans’ confidence in their most cherished ally.