Washington, July 18 (RHC)-- Amid escalating tensions with China over a number of issues, the United States has deployed two aircraft carriers to the South China Sea.

For the second time in two weeks, the USS Nimitz and USS Ronald Reagan conducted operations and military exercises in the waterway between July 4th and July 6th, and returned to the region on Friday, according to a U.S. Navy statement issued on Friday.

"Nimitz and Reagan Carrier Strike Groups are operating in the South China Sea, wherever international law allows, to reinforce our commitment to a free and open Indo-Pacific, a rules based international order, and to our allies and partners in the region," Rear Admiral Jim Kirk, commander of the Nimitz, said in the statement.

Relations between Washington and Beijing have been strained over the South China Sea and over the new coronavirus, trade, and Hong Kong.  The United States has threatened to impose sanctions on China over accusations of Beijing’s exploitation of offshore resources in most of the South China Sea.

The top U.S. diplomat for East Asia said earlier this week that Washington could respond with sanctions against Chinese officials and enterprises involved in what he claimed as coercion in the South China Sea. 

China says U.S. officials have “lost their minds and gone mad” in dealing with Beijing, in the strongest verbal reaction from China to the ratcheting up of tensions by Washington.

Earlier on Tuesday, Chinese Foreign Ministry spokesman Zhao Lijian had censured the U.S. rejection of China's claim, calling on Washington to stop its actions of disrupting regional peace and stability in the South China Sea.  “The United States is the destroyer and troublemaker to regional peace and stability. The international community sees it very clearly," Zhao said at a regular briefing.

"It intentionally stirs up controversy over maritime sovereignty claims, destroys regional peace and stability and is an irresponsible act," he added.

Some of the world's main water routes, where trillions of dollars worth of good are annually transited, pass through the South China Sea.  However, parts of the South China Sea, which are said to have untapped oil and gas reserves in them, are also claimed by China's neighboring countries, the Philippines, Brunei, Malaysia and Vietnam.

Beijing has constantly warned the U.S. against its military activities in the sea, saying that potential close military encounters by the air and naval forces of the two countries in the region could easily trigger accidents.