Visiting U.S. lawmakers are calling on Japan and South Korea to mend their relations, saying the trilateral alliance with the United States will only continue to grow in importance in dealing with regional challenges.

"As members of Congress, we are very concerned about strengthening the trilateral relationship," Rep. Diana DeGette, a Democrat from Colorado, told a news conference Tuesday in Tokyo, adding it is one of the "difficult issues that Japan will need to work through."

DeGette co-chairs the U.S. Congressional Study Group on Japan.

During the news conference, U.S. Ambassador Caroline Kennedy called for more people-to-people exchanges.

Japan's relations with China and South Korea remain frayed due to differences over perceptions of history and territorial disputes. Prime Minister Shinzo Abe's visit in December to Yasukuni Shrine, which honors convicted wartime leaders along with the nation's war dead, not just aggravated Japan's ties with its neighbors but also led the United States to express its disappointment.

"In terms of the security and economic situation, Japan and South Korea should not be arguing over anything," said Rep. James Sensenbrenner, a Republican from Wisconsin who is part of the bipartisan delegation. "I realize that there was a very, very tragic history that has occurred in the past. The time has come to put that in the past and anything that goes back to the bad memories prior to 1945."