Final approval of ON Semiconductor’s intended $2.4 billion purchase of Fairchild Semiconductor is now expected by mid-September.

The deal, which was announced last November and expected to close by Aug. 31, has been repeatedly extended. Last week, the Phoenix-based chipmaker got U.S. regulatory approval for the purchase from the Federal Trade Commission. ON Semiconductor offered to buy Fairchild, which employs about 650 people in South Portland, last December for $20 per share.

But it is still waiting for Chinese regulators to sign off. According to a company statement, the deal is now expected to conclude by mid month.

“ON Semiconductor and Fairchild continue to work expeditiously to obtain the remaining required regulatory approval in China in connection with the terms and conditions of the merger agreement and expect to close the acquisition around mid-September,” the statement said. Fairchild is based in San Jose, California, but operates a plant in Suzhou, China.

In an Aug. 26 interview with the Press Herald, Parag Agarwal, vice president of investor relations and corporate development for ON Semiconductor, said the company expected to receive approval from China “fairly soon.” He was optimistic at that point that the deal could be concluded by the end of August.

It is unclear what the sale will mean for the Fairchild plant in Maine, where analog switches, USB devices, converters, speedy circuit breakers and other building blocks of digital circuitry are made. Some semiconductor analysts have said the sale could make the Maine operation vulnerable to closure because it is dated, while other industry observers say the cost to build a chip-making factory from scratch is prohibitively expensive, which favors the continued operation of the Western Avenue facility.