Mark Lippert, the nominee for U.S. ambassador to South Korea, has excellent qualifications to take up the job and would well serve both nations if the Senate confirms his nomination, the State Department said Monday.

Lippert, chief of staff to Defense Secretary Chuck Hagel, was nominated in early May to replace Sung Kim as the top U.S. envoy to Seoul. The Senate Foreign Relations Committee held a confirmation hearing for him on June 18 and approved the nomination on June 24.

But his appointment has since been stuck in the Senate, along with dozens of others. And last week, Republicans in the Senate rejected calls from the committee's chairman for confirming Lippert's nomination, claiming he is a "political nominee."

"I would say that Mark Lippert, who has been the chief of staff at the Defense Department, has been a close adviser to the president, has served proudly his country in the military," State Department spokeswoman Jen Psaki said at a regular press briefing.

"I've had the pleasure of working with him on several occasions. I think his qualifications speak for themselves and South Korea and the United States would be well served having him there," she said in response to a request for comment on Senate Republications' refusal to endorse him.

The Senate went into recess for the month of August on Thursday.

Concerns have grown that Lippert's nomination could not be confirmed until after November's midterm elections because when the Senate reopens in September the session will last only 12 days. In addition, issues related to the midterm elections are expected to overshadow other matters from October.

Regardless of Lippert's confirmation, the outgoing ambassador, Kim, is expected to return to the State Department, sources said.

In that case, the post of U.S. ambassador to Seoul could be left vacant until Lippert's nomination is approved. (Yonhap)