South Korea's rival political parties denounced a senior U.S. diplomat Monday after she blamed both South Korea and Japan for their inability to come to terms with their shared history.

On Friday, U.S. Under Secretary of State Wendy Sherman said historical and territorial tension between South Korea, China and Japan are "frustrating" to the U.S as she stressed the importance of cooperation between Washington and the three Northeast Asian nations.

Both Korea and China suffered under the brutal Japanese rule.

Korea was colonized by Japan from 1910 to 1945, while some parts of China were also occupied by Japan in the early part of the 20th century.

"It's not hard for a political leader anywhere to earn cheap applause by vilifying a former enemy. But such provocations produce paralysis, not progress," she said during a seminar at the Carnegie Endowment for International Peace, a Washington think tank, in what appeared to be a reference to South Korea and China. "To move ahead, we have to see beyond what was to envision what might be."

Rep. Kim Eul-dong of the ruling Saenuri Party warned that Washington would soon lose its status as the world's police if it turns a blind eye to victim states.

"For stability and peace in Northeast Asia, the United States should abandon its vague stance and take a fundamental approach to conflict resolution," she said during a party meeting.

The main opposition party New Politics Alliance for Democracy expressed regret at Sherman's remarks and accused the South Korean government of incompetence.

"(Sherman's) complacent view is beyond regrettable and truly deplorable," Rep. Jun Byung-hun of the NPAD said during a party meeting. "I cannot help but blame our government's diplomatic incompetence."

Seoul's foreign ministry said that it has exchanged views with Washington's authorities over the issue, saying the U.S. notified Seoul that "There is no change in the U.S. stance over the history issue" involving Northeast Asia.

The U.S. has been supportive of previous Japanese governments' apologies for Tokyo's wartime sex slavery and its colonial rule. In April 2014, U.S. President Barack Obama called Japan's sexual enslavement of Korean women a "terrible and egregious violation of human rights."

But Sherman's recent remarks stirred controversy here as Washington may have changed its course due to its own interests by apparently tilting toward Japan, which is in talks with Washington over a U.S.-led trade deal dubbed the Trans-Pacific Partnership.

An official at the foreign ministry said that the U.S. has maintained the stance that countries in Northeast Asia need to develop future-oriented relations after healing the wounds from the past.

"We understand that Sherman's remarks were made based on this basic U.S. stance," the official said. "Sherman also mentioned in detail that Seoul is also Washington's ally and friend that shares core values with the U.S."

Vice Foreign Minister Cho Tae-yong told lawmakers that Seoul will deal with this issue "with a sense of gravity."

"Seoul's foreign ministry does not take her comments lightly,"

Cho said. "But the Korean government has found that there is no change in the U.S. stance over the history issue. The two countries plan to exchange views over the issue more closely (in the near term)." (Yonhap)