China can detect nuclear missiles launched from an enemy and counterattack using nuclear weapons within minutes before they land in the country, according to a paper written by a Chinese former military officer.

His remarks indicated China may have completed a missile attack early warning system while bolstering its nuclear programs, which could threaten the United States in security terms, foreign affairs experts said.

Development of the system requires advanced missile defense technologies integrating artificial satellites to detect missile launches with sea-based radar, they said.

China has apparently increased its missile defense capabilities in recent years, as the leadership of President Xi Jinping has stepped up efforts to give the nation's military "world-class" status by the mid-21st century.

The paper was written by Yang Chengjun, a Chinese specialist on nuclear missiles, who had long worked for the People's Liberation Army Rocket Force, which has a nuclear missile unit.

In the paper, Yang also emphasized that China's nuclear capacity has become comprehensively comparable to those of the United States and Russia.

China has so far pledged to pursue the policy of "no first use" of nuclear weapons under any circumstances.

The basic principle of its nuclear strategy is that the country would counterattack with the nuclear weapons remaining without being destroyed after being hit by the enemy's nuclear weapons.