U.S. Deputy Secretary of State Tony Blinken arrived in South Korea Sunday to discuss North Korea's nuclear issue and the Seoul-Washington alliance, government officials said.

The No. 2 official at the State Department, will stay in Seoul until Tuesday, the first leg of his trip to Asia that also includes stops in China and Japan. He took office in December after serving as U.S. President Barack Obama's deputy national security advisor.

Blinken plans to have talks with his South Korean counterpart Cho Tae-yong on Monday to discuss the North's nuclear issue and other bilateral and global matters, according to Seoul's foreign ministry.

His regional trip is aimed at advancing Washington's rebalancing to Asia policy and consulting with close allies of Seoul and Tokyo while building cooperation with China, Blinken said in a Twitter question and answer session on Friday.

Asked about China's opposition against THAAD deployment in South Korea, Blinken said that the missile defense on the Korean Peninsula possibly including THAAD would be directed against North Korea. THAAD refers to a Terminal High-Altitude Area Defense (THAAD), an advanced U.S. missile defense system.

He called Pyongyang's nuke weapons program "the greatest source of regional instability."

Seoul and Washington have been making a flurry of diplomatic efforts to show their strong alliance and close collaboration over North Korea's denuclearization.

His visit came as Wendy Sherman, U.S. undersecretary of state for political affairs, and Rose Gottemoeller, U.S. undersecretary of state for arms control and international security, visited Seoul in late January.

Sherman stressed there is "no daylight" between Seoul and Washington in dealing with North Korea, also expressing support for Seoul's bid for inter-Korean dialogue.

Despite the stalled multilateral denuclearization talks, the U.S. has not utterly shut the door on dialogue with the North. It recently attempted to have talks with the country but to no avail.

Sung Kim, Washington's top nuclear envoy, had offered to meet with North Korea's top nuclear negotiator in a third country during his recent trip to Asia, according to a diplomatic source. But the proposed meeting did not materialize as the North insisted on a meeting in Pyongyang. (Yonhap)