China’s land reclamation projects in the South China Sea have grown dramatically over the past few months and Beijing is patrolling the waters around its territorial claims to assert its power, according to a report issued by the Pentagon Thursday.

The Wall Street Journal, citing the newly released report, writes that China has reclaimed 2,900 acres of land mass across the Spratly Islands in the South China Sea as of June. The territorial claims are up 50 percent from May, according to the report.

The U.S. fears the islands will be used for military purposes and could pose a threat to one of the world’s biggest commercial shipping routes as China claims land in what other countries see as international waters, according to the newspaper. Defense officials also say China’s assertiveness poses a risk of possible confrontation with the U.S.

The report comes about a month before Chinese President Xi Jinping is scheduled to make a visit to Washington, where the South China Sea will be among the issues at hand. The report says China’s development in the region has accelerated considerably.

The U.S. has repeatedly questioned whether Beijing had ceased the land reclamation projects, as it claimed earlier this month. Chinese embassy spokesman Zhu Haiquan told The Wall Street Journal on Thursday the projects stopped in June and the facilities being built on the islands include those for public good.

“China stands ready to open these facilities to other countries upon completion,” Zhu said. “We hope the U.S. side will view this in an objective and balanced way and respect regional countries’ efforts to maintain the peace and stability of the South China Sea.”

Before this year, defense officials thought Beijing had only reclaimed about 500 acres of landmass to build the artificial islands. However, the lands are big enough for buildings and house equipment. One would be big enough to support a 3,000-foot runway.

Other Asian countries, including Brunei, Malaysia, the Philippines, Taiwan, and Vietnam, have laid claim to the islands as well. But China’s land reclamation projects have been more aggressive than those of its neighbors.

Vietnam has reclaimed 80 acres, Malaysia reclaimed 70 acres, the Philippines reclaimed 14 acres and Taiwan reclaimed eight acres, according to the Pentagon report.

China has also increased patrols on the disputed areas to “increase its effective control” over the islands, according to the report. China is also expanding the use of its Coast Guard to enforce its claims in the East and South China Seas.

The latest moves from China have some U.S. military officials pushing the Pentagon to be more aggressive in countering China in the region. They’ve wanted more assertive maritime and air patrols to fly within the 12 nautical mile territorial limit of some of the disputed lands China claims, according to The Wall Street Journal.

Earlier Thursday, Secretary of Defense Ash Carter said the military would fly and steam where and when it wanted, but it remained unclear whether they’ve flown within the 12 nautical mile zone of the islands.

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