(CNN) The Trump administration wants additional high-level talks with North Korea and assurances from Kim Jong Un that he is committed to giving up his nuclear program before next month's planned historic summit in order for the meeting to go ahead, a senior administration official involved in planning for the talks told CNN.

"We need to have more conversations about what we would be talking about before we know if this is going to be useful," the official said.

The official said substantive discussions before the summit would need to take place between North Korea's leadership, and either Secretary of State Mike Pompeo or other top administration officials after the completion of joint US-South Korea military exercises. North Korea had threatened to withdraw from the talks if the joint exercises proceeded or if the US continued to insist Pyongyang abandon its nuclear program, prompting concern in Washington about Kim's true intentions.

Pompeo said Tuesday he would "do what it takes to make sure that this is a successful meeting," including meeting with the North Koreans again, possibly in a third country.

"The key point is whether Kim Jong Un has made a decision to denuclearize. If he has, it should not be that difficult to reach agreement," the official said. "If he hasn't and plans to play the same game he did during the Agreed Framework or the Six Party Talks, then it's not going to work. We don't know the answer to that. If the communications lines open again, we may well know before anyone leaves for Singapore."

Read More