South Korean National Assembly Speaker Chung Ui-hwa sent a letter to the U.S. House speaker Thursday, expressing sympathy over the bloody attack on the U.S. ambassador to Seoul and vowing to work harder to further strengthen the alliance between the two countries.

"It is a firm resolution of the Republic of Korea that this kind of terrorism can never be tolerated," Chung said in the letter to John Boehner (R-OH). "Any attempt to hurt the Korea-U.S. alliance won't succeed in the Republic of Korea."

Chung also said South Korean legislators and citizens "stand with Amb. Mark Lippert and his family." He also said the South Korean National Assembly will work harder together with the U.S. Congress to move the alliance forward.

"I join citizens of the Republic of Korea in wishing Amb.Lippert a speedy recovery," he said.

A knife-wielding assailant slashed Amb. Lippert on the face and wrist at a breakfast function in central Seoul. The ambassador was immediately taken to a hospital and received more than 80 stitches.

Hospital officials said he will need to remain hospitalized for three to four days.

The attacker was immediately arrested. As he was hauled away, Kim shouted his opposition to joint military exercises under way between South Korea and the U.S. North Korea has strongly condemned such annual drills as a rehearsal for an invasion of the country.

Earlier in the day, Chung condemned the attack.

"This is appalling. Can we imagine an ambassador of our country being attacked like this at a public occasion in an ally country?"

Chung was quoted as saying by his spokesman, Choi Hyung-du.

"Terrorist violence can never be tolerated in a free democracy."

Chung also urged the South Korean government to beef up security measures for foreign diplomats.

Chung has been in Washington since Tuesday for discussions with Boehner and other congressional leaders about ways to mark the 70th anniversary of the end of World War II and Korea's liberation from Japan's 1910-45 colonial rule.

During a meeting with Boehner on Wednesday, Chung proposed that the U.S. Congress join South Korea in adopting a resolution calling for peace in Northeast Asia and the peaceful unification of the Korean Peninsula. Boehner responded favorably and said he looks forward to working with the South Korean parliament.

It was the first meeting between the parliamentary speakers of the two countries since 2005.

Chung also attended a lunch meeting hosted by Rep. Ed Royce (R-CA), chairman of the House Foreign Affairs Committee. Others attending the lunch included pro-Korean lawmakers Charles Rangel (D-NY) and Mike Honda (D-CA). (Yonhap)