WASHINGTON -- The US-South Korea alliance is an incredibly important relationship that is vital to many issues in the region and around the world, a White House spokesperson said Monday of reasons for President Joe Biden's planned trip to Seoul.

Jen Psaki also noted North Korea will be a "prominent part" of the agenda for Biden's upcoming trip that will also take him to Japan.

"I would note that we have an incredibly important, vital relationship with South Korea. We work on a range of issues in the region and around the world, and that is the reason why the president is going to be visiting later this month," she said in a press briefing when asked if the US plans to invite South Korea to join the Quadrilateral Security Dialogue, a grouping of the US, Australia, Japan and India.

"There are many ways that we engage with South Korea. It's an incredibly important partnership, relationship, but the Quad will remain the Quad. We will continue to engage with South Korea through a range of mechanisms and continue to work on the strength of our relationship," she added.

The White House earlier said the US leader will be traveling to South Korea and Japan, in that order, from May 20-24.

Psaki said the order of Biden's trip should not be over emphasized when asked if his visit to Seoul before Tokyo indicates the US' focus on North Korea issues.

"In terms of the order of the trip. I would not over read into that. Obviously we have a strong relationship with Japan, strong relationship with South Korea," she said, adding, "I'm certain North Korea will, of course, be on the agenda, prominent part of the agenda."

Pyongyang has staged more than a dozen rounds of missile launches since September, while remaining unresponsive to US overtures since the Biden administration took office in January 2021. (Yonhap)