The United States and Japan should act with caution regarding the South China Sea issue, a Foreign Ministry spokeswoman urged on Friday, emphasizing China's resolve to defend its territory.

Spokeswoman Hua Chunying commented after the US and Japan issued a joint statement expressing "serious concerns" on the issue. The two countries released the statement after Japan's foreign and defense ministers met in Washington on Thursday with the US secretaries of state and defense.

Hua said the US and Japan are not parties concerned with the South China Sea issue. "They should have been cautious with their words and actions and respected efforts the regional countries have made to resolve the disputes."

The situation in the South China Sea is becoming stable and has improved, with talks between China and countries of the Association of Southeast Asian Nations making progress, Hua said.

China and ASEAN countries this month adopted the Framework of a Code of Conduct in the South China Sea at the China-ASEAN Foreign Ministers' Meeting in Manila.

The statement also touched on China's Diaoyu Islands by reconfirming that Article 5 of the US-Japan security treaty applies to the islands.

"The so-called treaty is a product of the Cold War era, which should not be used to endorse Japan's illegal claims, and must not violate China's territorial integrity and relevant rights," Hua said.

Hua, who expressed China's "serious concern" over the statement, added, "China's position on the Diaoyu Islands and the South China Sea issue is consistent and clear. The Chinese government and people stand unswervingly in their resolve and will to safeguard their territorial sovereignty."

Hua urged the US and Japan to adopt a responsible attitude and to do more for regional peace and stability.