The No. 1 challenge the United States is facing right now is how to cope with threats posed by North Korea and China, Republican presidential runner Marco Rubio said.

Rubio made the remark during a Republican presidential candidate debate Saturday night, putting the North Korean issue ahead of Middle Eastern problems and tensions with Russia.

"I think there are three major threats that you want to immediately get on top of. No. 1 is, what are we doing in the Asia-Pacific region, where both North Korea and China pose threats to the national security of the United States," Rubio said.

The No. 2 threat is the Middle Eastern problems, including the threat of the militant group Islamic State, and the third challenge is to rebuild and reinvigorate NATO in Central and Eastern Europe, where Russia is threatening the territory of multiple countries, Rubio said.

Rubio is considered most active on North Korea issues among all U.S. presidential candidates. He has made a series of strong remarks on the communist nation since Pyongyang's fourth nuclear test followed by a long-range missile launch.

The Florida senator co-sponsored a North Korea sanctions bill led by Sen. Cory Gardner (R-CO) last October. The legislation, which was later combined with a similar House bill, overwhelmingly passed the Senate and the House last week.

Rubio has also called for relisting the North as a state sponsor of terrorism. (Yonhap)