North Korean leader Kim Jong Un on Tuesday signed an agreement that “reaffirmed his firm and unwavering commitment to complete denuclearization of the Korean Peninsula.”

That may sound promising, but many experts warned ahead of the historic summit between Kim and U.S. President Donald Trump that North Korea likely has a different understanding of what denuclearization entails.

For the U.S., the term means North Korea giving up its nuclear weapons — but Pyongyang may agree to do so only if certain conditions are fulfilled.

Possible conditions include ending the American military presence in South Korea. It may also mean scrapping the U.S. regional nuclear umbrella, an arrangement under which Washington promises to retaliate if its allies are attacked with nuclear weapons.

North Korea’s concept of denuclearization, made clear through years of failed discussions with the international community, “bears no resemblance to the American definition,” Evans J.R. Revere, a nonresident senior fellow at Brookings, wrote in a note.

In agreeing to meet with Trump, Kim resuscitated the approach his country has pursued in previous negotiations, Revere warned.

In their agreement, the United States “committed to provide security guarantees” to North Korea. Both leaders committed to “follow-on negotiations.”

For North Korea, denuclearizing the peninsula means it gives up nukes if the United States ends its alliances in Asia and pulls ground troops out of South Korea, Victor Cha, a Georgetown University professor and senior advisor at the Center for Strategic and International Studies, said at a Washington event before the summit.

Negotiators in Trump’s administration should seek a written commitment that North Korea will abandon all nuclear weapons and existing nuclear programs, Cha said at that time.

The document signed on Tuesday doesn’t include that language, but it does commit to further talks.