U.S. Vice President Joe Biden says efforts to enforce the Nuclear Nonproliferation Treaty (NPT) have resulted in the imposition of the most restrictive U.N. sanctions resolution to date on North Korea.

Speaking at the National Defense University in Washington on Thursday, Biden said that the U.S. will work to reinforce the NPT consensus and to strengthen the treaty for the future.

Biden said the U.S. will do everything in its power to prevent the spread of nuclear weapons to terrorists and also to states that do not already possess them.

He said the U.S. will build momentum for collaboration with Russia on strengthening the global consensus that nations who violate their NPT obligations should be held to account.

Biden added that the U.S. is now working with its international partners to ensure that Iran, too, faces real consequences for failing to meet its obligations.