The spat between China and Vietnam over an oil rig in the South China Sea has become increasingly ugly. But a Chinese official said Friday that China will never send its military to the scene of the conflict, and accused Hanoi of attempting to force an international lawsuit, Reuters reported.

Vietnamese and Chinese ships, including coast guard vessels, have confronted one another around the rig. There has been a series of collisions after the Chinese platform was towed into disputed waters in early May.

The rig's deployment triggered anti-Chinese riots in Vietnam in May that led to the death of at least four workers.

A senior U.S. official in Washington dismissed the Chinese statement as "patently ridiculous" and claimed that Beijing had been using its air force and navy, not to mention coast guard assets, "to intimidate others," according to the news agency. The U.S. hasn't taken a side in the disputes, but it has been quite critical of China's behavior and called for negotiations.   

Vietnam accused China of sending six warships. However, Yi Xianliang, deputy director-general of the Ministry of Foreign Affairs' Department of Boundary and Ocean Affairs, said China had never sent military forces.

"I can tell you very clearly that from May 2 to today, including to when the [drilling] operations are complete, we have never, are not and will never send military forces. Because we are carrying out normal, civilian, commercial activities," Yi told a news conference.

"What I can tell you is that this is on a maritime route and at some periods there have been certain Chinese military ships coming back from the south but these have been far away" from where the standoff around the rig has been taking place, he added.

About 90 percent of the South China Sea is claimed by China, but parts of what could potentially be an energy-rich body of water are also subject to claims by the Vietnam, the Philippines, Malaysia, Brunei and Taiwan.

Beijing stations military forces on several of the islands it occupies in the Spratly and Paracel Island groups in the South China Sea.

According to Reuters, the Haiyang Shiyou 981 rig is drilling between the Paracel Islands and the coast of Vietnam, which said that the rig is in its 200-nautical-mile exclusive economic zone and on its continental shelf. China says it is operating within its waters.

The senior U.S. official called Yi's statement "a weak attempt to obscure what China is really doing."

"China has maintained a robust and consistent military presence near the oil rig since its placement on May 2, including flying helicopters and planes over and around the rig. There are currently multiple military vessels in the vicinity of the rig," he said. He also said China’s actions were "creating serious frictions" with Washington.

Last month, Vietnam's prime minister, Nguyen Tan Dung, told Reuters that Vietnam was contemplating a number of "defense options" against China, including legal action -- a move the U.S. has said it would support.