WASHINGTON — The United States and China on Friday escalated their dispute over contested territory in the South China Sea, after the Chinese repeatedly ordered an American military surveillance plane to abandon flights over areas where China has been building artificial islands.

The continued American surveillance flights in areas where China is creating new islands in the South China Sea are intended to challenge the Chinese government’s claims of expanded territorial sovereignty. Further raising the challenge, Pentagon officials said they were discussing sending warships into waters that the United States asserts are international and open to passage, but that China says are within its zone of control.

The Defense Department planning comes in response to China’s accelerated efforts to build new islands in the South China Sea to bolster claims to a vastly expanded area of sovereignty, a direct challenge to the United States and other nations in the region.

The Chinese government expressed “strong dissatisfaction” with the surveillance flights, while urging the United States to cease actions that they said risked increasing tensions. Hong Lei, the Foreign Ministry spokesman, warned that the American flights, which he called “very irresponsible and dangerous,” were “likely to cause an accident.”