The Trump administration will not insist on a complete accounting of North Korean nuclear-related assets ahead of a second summit between President Trump and North Korean leader Kim Jong Un, Vice President Pence acknowledged Thursday.

Pence was asked whether a “complete list” of North Korean weapons and facilities was a condition for a summit envisioned for early next year.

“I think it will be absolutely imperative in this next summit that we come away with a plan for identifying all of the weapons in question, identifying all the development sites, allowing for inspections of the sites and the plan for dismantling nuclear weapons,” Pence said in an interview with NBC News.

The listing of nuclear weapons and related sites has been a holdup in talks between the United States and North Korea, which continues to develop its nuclear program despite what Trump has called a commitment to give up weapons.

The White House has said the accounting is an essential first step toward what Trump claims is a shared goal of “complete, verifiable, irreversible denuclearization of the Korean Peninsula.”

Veterans of negotiations and administration critics say North Korea is unlikely to ever provide an accurate listing and to ever completely abandon its weapons program.

Speaking in Singapore, where Trump and Kim first met five months ago, Pence said the next Trump-Kim summit must produce a “verifiable plan” to disclose sites and weapons.

“Now we need to see results,” Pence said.

North Korea postponed scheduled meetings last week in New York, where Secretary of State Mike Pompeo was expected to press for the accounting.

The Trump administration has criticized past U.S. administrations for reaching agreements that North Korea promptly broke after receiving economic or other concessions.

Tough U.S. sanctions on North Korea will remain in place until there is more progress, Pence said in the interview. The administration denies that it is being strung along by North Korea in much the same fashion as previous U.S. administrations.

A Center for Strategic and International Studies report this week claims there are an estimated 20 undeclared missile operating bases that Pyongyang has continued to develop since Trump and Kim met in June.

Pence is attending the 6th ASEAN-U.S. Summit on the sidelines of the 33rd Association of Southeast Asian Nations (ASEAN) Summit and Related Meetings on Thursday in Singapore.