South Korean President Moon Jae-in called for efforts to further strengthen the Korea-US alliance Monday, which he called the foundation of peace on the Korean Peninsula and in the Northeast Asian region.

"I thank you for your efforts for peace on the Korean Peninsula and in Northeast Asia," the president said, while meeting with a bipartisan group of US lawmakers at his presidential office Cheong Wa Dae in Seoul.

"I especially thank you for imposing strong sanctions and pressure on North Korea through legislation for its continued nuclear and missile provocations, while also sending a message of a diplomatic solution at the same time," he added, according to Cheong Wa Dae pool reports.

The visit by the US delegation, led by Ed Royce (R-CA), came two days after North Korea fired a series of what appeared to be short-range missiles in a clear protest against a joint military exercise of South Korean and US forces here in South Korea.

The latest missile launch marked the 13th of its kind since the beginning of the year and the eighth since the new South Korean leader took office May 10.

Moon reiterated the need to apply what he called "maximum pressure and sanctions" on North Korea, but only for now.

"North Korea's complete nuclear dismantlement must ultimately be achieved through dialogue," he said, according to Cheong Wa Dae spokesman Park Soo-hyun.

He also stressed the need to thoroughly verify the North's denuclearization process should the communist state decide to give up its nuclear ambitions.

"Even if North Korea takes phased steps for nuclear dismantlement, each step in each phase must be thoroughly verified and steps in each phase must be taken in irreversible ways," Moon was quoted as saying.

Royce, chairman of the US House Foreign Relations Committee, agreed on the importance of the Korea-US alliance, calling it a cornerstone of his country's diplomatic and military presence in the area.

The US delegation included four other representatives. They were Ted Yoho (R-FL), Ami Bera (D-CA), Brad Schneider (D-IL) and Jennifer Gonzalez (R-PR).

President Moon asked for their support in further strengthening the Korea-US alliance.

"I ask you to once again confirm the friendship of the Korean people and provide your support for closer development of the Korea-US alliance," he told the meeting.

Seoul and Washington are currently moving to modify their free trade agreement at the request of the United States, which argues the bilateral free trade pact that went into effect in March

2012 has led to a significant increase in its trade deficit with South Korea.

Moon, who has insisted the Korea-US FTA has mutually benefited both countries, said it was the most advanced FTA signed by the United States with an Asian state so far, according to the Cheong Wa Dae spokesman.

"We will work to make sure the two countries will mutually develop through the Korea-US FTA," Moon told the meeting.