BEIJING, July 16 -China Railway Corp. (CRC) plans to buy 351 bullet trains via tender in August that it estimated would cost 66 billion yuan as the operator of the country's railroads continues to add to its high-speed network.

The CRC issued a notice on July 15 that invited bidders for 98 250 kph trains; 196 that travel at up to 300 kph; and 12 more that run at up to 350 kph. The company also said that it will buy 45 high-speed trains capable of operating at high altitudes and low temperatures.

Manufacturers have until 2:30 p.m. on August 6 to place their bids, the CRC said. Each train will include one engine and and unspecified number of cars. Bullet trains in the country often have six to eight cars.

The CRC budgeted around 150 billion yuan for train and parts procurement in 2015, but only spent 30.9 billion yuan in the first half of the year.

The tender comes as the CRC continues to add to the country's bullet-train network. Some 1,000 kilometers of track were added to the network in the first half of the year, bringing the total to 17,000 kilometers.

Analysts and media outlets have questioned whether the tenders will become a formality now that two country's main train makers merged into China Railway Rolling Stock Corp. Ltd. in June.

However, a manager at one equipment supplier who asked not to be named said the new company had three subsidiaries licensed to make high-speed trains and they will have to compete as separate entities because they are independently run.

The former Ministry of Railways bought 1,300 high-speed passenger trains from 2004 to 2010 as China rapidly expanded its railroad network. In 2013, the ministry was ordered by the central government to split in two, becoming the CRC and the National Railway Administration, which is under Ministry of Transportation.

The procurement of high-speed trains was mostly stopped until 2013 following an accident in which two high-speed trains collided in Wenzhou, in the eastern province of Zhejiang, killing 40 on July 23, 2011.

The CRC bought 349 passenger cars in two tenders in 2013, and the next year two more tenders involved 393 trains. This makes this year's purchase the biggest single tender for the CRC.

China's high-speed trains are based on imports from Germany and Japan. Foreign companies have been shut out of CRC tenders since 2007, the year Chinese suppliers started making their own trains.