U.S. President Barack Obama said on Thursday that U.S. commitment to South Korea’s security and defense will never waver, warning Pyongyang of "even more pressure and isolation" if it continues to ignore international obligatio

U.S. President Barack Obama said on Thursday that U.S. commitment to South Korea's security and defense will never waver, warning Pyongyang of "even more pressure and isolation" if it continues to ignore its international obligations.

Calling South Korea "one of our strongest allies", Obama told reporters at the White House that "I can never say it enough, the commitment of the United States to the defense and security of the Republic of Korea will never waver."

He said he discussed the situation on the Korean Peninsula with his South Korean counterpart Lee Myung-Bak, saying Pyongyang" continues to pose a direct threat to the security of both our nations."

He warned that "If Pyongyang continues to ignore its international obligations, it will invite even more pressure and isolation."

"If the North abandons its quest for nuclear weapons and moves toward denuclearization, it will enjoy greater security and opportunity for its people," he added.

Obama vowed to maintain strong U.S. presence in the Asia- Pacific, calling it "a foundation for security and prosperity in Asia in the 21st century."

President Lee, who appeared at a joint press conference with Obama after bilateral talks at the White House, said that his country will continue to work toward denuclearization of the Korean Peninsula.

"For North Korea, the only way to ensure happiness for its people and to embark on that path to development is to abandon its nuclear ambitions," he said. "And so we have tried through peaceful means, through diplomatic means to strongly urge North Korea to abandon its nuclear ambitions."

He vowed to continue to "speak with one voice" with the U.S. on the issue of denuclearization of the Korean Peninsula, saying the alliance between South Korea and the U.S. "guarantees peace, stability and prosperity on the Korean Peninsula, the Asia-Pacific region and beyond."

The Democratic People's Republic of Korea (DPRK) quit the six- party talks over its nuclear program in 2009, and a series of events had taken place since and strained ties between the two sides on the Korean Peninsula.

DPRK has vowed to continue its cooperation with all the parties concerned for an "unconditional resumption of the Six-Party Talks," a mechanism that also involves China, the U.S., Russia and Japan.