The United States called on North Korea to refrain from destabilizing actions after a senior Pyongyang diplomat said the U.S. has "crossed the red line" and declared war on the communist nation.

Han Song-ryol, director-general of the U.S. affairs department at the North's Foreign Ministry, made the remark, blasting the U.S. imposition of sanctions on North Korean leader Kim Jong-un for his roles in the country's human rights abuses, according to AP.

"The Obama administration went so far to have the impudence to challenge the supreme dignity of the DPRK in order to get rid of its unfavorable position during the political and military showdown with the DPRK," Han was quoted as saying.

"The United States has crossed the red line in our showdown ... We regard this thrice-cursed crime as a declaration of war," he said.

Han was also quoted as warning that a vicious confrontation could erupt if the U.S. and South Korea hold annual military exercises as planned next month. The North has long claimed such routine drills are part of preparations to invade the country.

In response, State Department spokesman John Kirby renewed the usual call for restraint.

" I think what I would say is the same thing we've said, that it's time for the DPRK to cease rhetoric and to cease actions that only, you know, serve to destabilize the peninsula and do nothing to improve the lives of the North Korean people," Kirby said.

The North has been upset not only by the sanctions on its leader, but also by decision by Seoul and Washington to deploy a THAAD missile defense battery in the South, which Pyongyang denounced as part of a plot to invade the country.

A day after the THAAD deployment decision was announced, the North tested a submarine-launched ballistic missile. Last week, the North also fired three short- and intermediate-range ballistic missiles in an exercise that Pyongyang said was aimed at striking American forces in South Korea. (Yonhap)