BEIJING (AP) ― At an “appropriate time,” China will send a team to survey islands at the heart of an increasingly heated dispute with Japan, a Chinese official said Tuesday in Beijing’s clearest statement yet that it intends to set foot on the Japanese-controlled territory.

The remarks by Chinese mapping agency Vice Director Li Pengde added to the sharpening rhetoric between the two sides over a set of uninhabited islets known as Diaoyu in Chinese and Senkaku in Japanese. The dispute has greatly increased tensions between the world’s No. 2 and No. 3 economies.

In an interview with state broadcaster CCTV, Li said China plans to send a team to go onto the islands and study their layout. Surveying by land would allow the mapping of caves and other features not visible from the air, Li told the station.

He said, without elaborating, that the team would arrive at an “appropriate time.”

“My hope is that we can get under way under conditions where the situation is relatively good and the survey team’s physical safety can be assured,” Li said. 

The islands are the focus of a decades-long dispute that reignited in September, when the Japanese government purchased three of the islands from their private owners. The move had been intended to prevent the islands from being bought by Tokyo’s former nationalist mayor, who wanted to build a dock there for Japanese fishing boats and also backed sending experts to the islands to study their wildlife and terrain.

The purchase prompted anti-Japanese protests in China, and Beijing has regularly sent ships to confront the Japanese coast guard in the area since tensions spiked.

Seeking to avoid further controversy, Japan’s Coast Guard forbids anyone of any nationality from landing on the islands, including Japanese and Chinese nationalists seeking to plant flags there.

The chain is made up of five main islands with a total area of just over 6 square kilometers, covered in rock, scrub brush and seabird habitat. They have been uninhabited since 1940, when a fish processing plant on the main island closed, and were under U.S. administration from the end of World War II until 1972, when they were returned to Japanese control.

Although China’s claim to the islands is based on its interpretation of historical records, it has sought to use cartography to support that by issuing a series of maps last year that ascribed place names to even the smallest rocks and outcroppings.