BEIJING - A Foreign Ministry spokesperson urged the United States to be "frank and forthright" in the South China Sea issue on Thursday.

Spokeswoman Hua Chunying's remarks at the ministry's regular press briefing came in response to a question on U.S. Secretary of Defense Ash Carter's visit to U.S. aircraft carrier USS Theodore Roosevelt in the South China Sea on the same day.

China is opposed to any actions leading to militarization of the South China Sea that pose a threat to other country's sovereignty and security interests in the name of freedom of navigation and overflight.

China has never been opposed to other countries' legitimate rights in real international waterway, she said. The country respects and safeguards other countries' freedom of navigation in the region under international law.

The U.S. should be more open and transparent on the issue, said the spokeswoman.

Last week, U.S. warship USS Lassen entered waters near Zhubi Reef, which is part of China's Nansha Islands in the South China Sea, without permission from China, offending the Chinese government and military leadership.