South Korea, the United States and Japan agreed Thursday to step up joint efforts to increase pressure on North Korea after the communist nation threatened that it's close to perfecting a long-range ballistic missile.

South Korean Vice Minister Lim Sung-nam, US Deputy Secretary of State Antony Blinken and Japanese Vice Foreign Minister Shinsuke Sugiyama reached the agreement when they held the last round of deputy-level trilateral consultations under the outgoing US administration.

"South Korea, the US and Japan agreed to further strengthen joint efforts aimed at making North Korea have no choice but to step forward toward meaningful denuclearization," Lim said during a joint news conference with Blinken and Sugiyama after the talks.

Lim said the North is challenging head-on international demands for denuclearization.

In a joint fact sheet adopted at the talks, the three countries said the "complete, verifiable and irreversible denuclearization of North Korea remains the only viable option to safeguard peace and security."

"North Korea's provocations only serve to deepen its isolation," it said.

The three countries will work together with other partners around the world for full implementation of UN sanctions, the document said.

"These sanctions, along with our close trilateral coordination on our respective new unilateral sanctions against North Korea, are the latest steps in our ongoing efforts to convince North Korea that the only path to the economic development and international recognition it claims to seek is by returning to credible and meaningful negotiations on denuclearization," it said.