KUALA LUMPUR, Malaysia >> In a direct challenge to China, U.S. Secretary of State John Kerry called Thursday for all claimants to disputed territories in the South China Sea to immediately halt provocative activities that have ratcheted up tensions in some of the world’s busiest shipping lanes. He also said the United States would not accept restrictions on navigation or overflights of the disputed territories

In remarks to East Asian foreign ministers in Malaysia, Kerry proposed a joint commitment from all involved to halting land reclamation projects and construction, which he said would lower tensions and risks for miscalculation. He said the step would also create space to finalize a binding code of conduct. His comments were directed primarily at China, which has been engaged in massive reclamation projects in areas contested by its smaller neighbors. China has rejected outside interference in the disputes.

"With great respect to my friend and colleague (Chinese) Foreign Minister Wang (Yi), the United States and others have expressed concern to China over the pace and scope of its land reclamation efforts," Kerry said. "And the construction of facilities for military purposes only raises tensions and the destabilizing risk of militarization by other claimant states."

Kerry complained that China has not lived up to pledges to ease tensions and to not try to exert control over South China Sea navigation or flights. And, he said he could not confirm Chinese protestation that it has stopped land reclamation projects. "I hope it is true," he said. "I don’t know yet."

But he added that the protests rang hollow because China is continuing construction projects, including military ones, on reclaimed land.

"It is not just an issue of reclamation," Kerry told reporters after his comments to the ministers. He added that he was not yet convinced that China had softened its stance. Wang, Kerry said, had "indicated a different readiness of China to try to resolve some of this, although I think it is still not as fulsome as some of us would like to see."

In order to calm the situation, Kerry said the U.S. was urging "all claimants to make a joint commitment to halt further land reclamation and construction of new facilities or militarization on disputed features."

"Such steps would lower tensions and create diplomatic space for a meaningful Code of Conduct to emerge by the time our leaders meet here in November," he said, referring to an East Asia Summit that will be held this fall.

At the news conference, Kerry added, "I reaffirmed that the United States has very strong interests in the South China Sea. The United States will continue to take steps to support peace and stability in this region."

And he said the U.S. would not back down on its support for freedom of navigation and overflight.

They "are among the essential pillars of international maritime law," he said. "Despite assurances that these freedoms will be respected, we have seen warnings issued and restrictions attempted in recent months. Let me be clear: The United States will not accept restrictions on freedom of navigation and overflight, or other lawful uses of the sea. These are intrinsic rights that we all share. It doesn’t matter whether a vessel is a large warship or a tiny fishing boat. The principle is clear: The rights of all nations must be respected."

Kerry’ s comments came a day after he and Wang clashed over who is to blame for rising tensions over territorial disputes in the South China Sea. Wang sent a strong message that those without claims, such as the United States, should allow China and the other claimants to deal with them on their own.

Chinese land reclamation in contested waters has irked Southeast Asian nations who, like the U.S., want China to stop. The U.S. is not a party to the conflict but says a peaceful resolution of the problem and freedom of navigation are in the U.S. national interest.

China rejects any U.S. involvement and insists it has the right to continue the reclamation projects. Beijing was opposed to the issue being raised at the security forum in the first place.

The disputes have led to deadly confrontations between China and Vietnam, and Washington and governments in the region are concerned that greater military deployments increase the risk of miscalculations and accidental clashes that could spiral out of control.

U.S. officials say China has reclaimed more than 3,000 acres (1,200 hectares) in the last 18 months alone. That figure dwarfs the 100 acres (40 hectares) that Vietnam, Malaysia, the Philippines and Taiwan have reclaimed in disputed areas over the last 45 years.