BANGKOK — A project to connect three international airports by high-speed rail was suspended after the conglomerate backing the project changed its terms.

The official who helped oversee the project, which would link Bangkok’s two airports with one on the eastern seaboard, said Charoen Pokphand Group, or CP, unexpectedly demanded doubling its operating concession from 50 to 99 years.

Kanit Sangsubhan, who’s managing the development of a new eastern economic region, said the conglomerate is also asking the government to guarantee a minimum profit of 6 percent annually.

“Let me clarify that such proposals cannot be accepted,” Kanit told reporters.

The official said those two demands were not part of the project when it went out to bid in December. CP, which owns a wide range businesses from agriculture to media, secured the project by asking for the least amount of state funding.

Of the 224 billion baht needed for construction, CP said it would only seek 117 billion baht from the government.

If completed, the high-speed railway would run between the Suvarnabhumi, Don Mueang and U-Tapao airports.

In its original government filing, CP said the firm has a 70 percent stake in the project, while construction firms Chor Karnchang and Italian-Thai own 15 percent and 5 percent, respectively. A Chinese company also owns 10 percent.

If CP presses the new conditions and negotiations fail, the company that manages the capital’s BTS Skytrain would be brought on board, Kanit said. The Bangkok Mass Transit System Co. Ltd. was the second most affordable bid after that of CP.