North Korea agreed Friday to work with South Korea to peacefully resolve the international standoff over Pyongyang's nuclear programs, as U.S. envoys stepped up diplomatic efforts elsewhere. But after the two Koreas issued a joint statement pledging cooperation, the South Korean government acknowledged that the agreement fell short of commitments it sought from the North during the Cabinet-level talks. In the declaration, the two sides said they had "sufficiently exchanged" positions on the nuclear issue and "agreed to actively cooperate to resolve this issue peacefully." Meanwhile, a top American diplomat visited Tokyo to strengthen international support for putting the issue before the U.N. Security Council. The push comes as top officials in Washington say they detect a softening in North Korea's stance.