Thailand’s two largest mobile operators announced plans to skip the country’s upcoming 900MHz spectrum auction, which could further delay the proceeding.

The country’s number one operator, AIS, revealed its decision in a filing with the Stock Exchange of Thailand. The company said it “took into consideration the auction terms and conditions, financial and investment evaluation, as well as benefits to our customers” before ultimately choosing not to participate.

True Corp, Thailand’s second largest operator, sent a similar notice to the stock exchange, but did not detail its reasoning for skipping the proceeding. The third major operator in the country, dtac, is yet to declare whether it will take part. Earlier this month the company picked up bidding documents for the auction, but said it would conduct a feasibility assessment before committing.

The decisions come despite attempts by Thailand’s National Broadcasting and Telecommunications Commission (NBTC) to drum up more interest in the auction by changing a key condition requiring winners to prevent interference with future railway projects in the band. The 900MHz auction was previously cancelled after all three operators opted out of the process.

NBTC previously noted it would push back the auction start date from 20 October to 28 October if only one operator participates.

In a stock market filing dtac stated that since it is the only one submitting an application for spectrum licences by the 9 October deadline, the period to submit the application will be extended as specified by the NBTC, and dtac will inform the stock exchange of its decision on the matter by 16 October.