SEOUL (THE KOREA HERALD/ASIA NEWS NETWORK) - South Korea and the US are now holding a joint military exercise.

The computer-based "Combined Command Post Training" does not involve massive numbers of troops and weapons, but the latest developments surrounding it raise some fundamental questions about the security alliance between Seoul and Washington.

The low profile of the exercise reflects the atmosphere of a thaw on the Korean Peninsula following a series of summit meetings North Korean leader Kim Jong-un had with South Korean President Moon Jae-in and US President Donald Trump.

Despite the thaw, however, North Korea has not changed its position on the South Korea-US joint drills.

In the weeks running up to the ongoing drill, the North fired a series of projectiles, including new types of guided rockets and short-range ballistic missiles. Pyongyang made it clear that the acts were a "warning" to the Seoul government.

It is not unusual for the North to react sensitively to a joint military manoeuvre between the allies, but it is noteworthy that Pyongyang's ire was directed only at Seoul this time.

In fact, instead of resorting to its usual vitriol against Washington, Kim sent a letter to Trump.

As usual, Trump is using the letter to brag about his "good relationship" with Kim and his still half-baked deal for denuclearisation talks with the young dictator.

Trump said last week that in another "very beautiful" letter he received, Kim said he wanted to resume the denuclearisation talks once the joint exercise between the US and South Korea is over.

Trump noted Kim "wasn't happy with the war games on the other side with the US."

This shows that one of Kim's purposes for writing to Trump was to achieve the North's long-held goal of ending South Korea-US joint military drills.

What startled us in the South, living under an immediate security threat from the North, is that Trump virtually echoed Kim's words in opposing the South Korea-US joint drills.

"As you know, I've never liked it either," Trump said. He said that he didn't like paying for the drills and that the US should be reimbursed for it.

We already know what kind of a man Trump is and how he abused his "America First" policy at the expense of key global and regional priorities.

It is still disappointing, however, to hear that the leader of a country responsible for protecting freedom and democracy in the world continues to put money ahead of anything else.

Another big concern regarding Trump's handling of North Korea is that it now seems that he virtually endorses the North's continuing missile tests.

Trump, who had already downplayed the North's recent short-range missile launches on the grounds that they do not target the US mainland, said that in his latest letter Kim made "a small apology" for testing the short-range missiles and vowed to stop them when the exercises end.

A North Korean statement was quick to take advantage of Trump's position, saying that "even the US president made a remark which in effect recognises the self-defensive rights of a sovereign state."

The statement also repeated Trump's past comment that a lot of countries do small-range missile tests. It looks like Trump and Kim are hitting it off with each other.

That the US president seems to share thoughts more with the North than the South on matters like the joint drills and the North's missile provocations could put public trust in decades long Seoul-Washington alliance in jeopardy.

Needless to say, the South Korea-US military drills, and more broadly the two countries' security alliance forged after the Korean War, are necessary not only for defending South Korea from a North Korean invasion, but also for maintaining peace and stability in this part of the world.

The recent incursion of the Chinese and Russian military aircraft into the South Korean and Japanese air defence identification zones is proof that a military alliance between the two countries, and Japan as well, is important and should be firmly in place at any cost.

While speaking about the contents of Kim's "beautiful" letter, Trump called the South Korea-US joint drills "ridiculous and expensive." It is sad that we may have to brace for more ridiculous statements from the US leader that could make the all-important alliance pay a heavy price.

The Korea Herald is a member of The Straits Times media partner Asia News Network, an alliance of 24 news media organisations.