China hopes to start the construction of a controversial high-speed rail project in Thailand that has been dogged by delays and public opposition by the end of the year.

The lone remaining hurdle to starting the first phase of the joint railway, which has an estimated price tag of US$5.2 billion, is the completion of an environmental impact assessment, according to Liang Xiaoguang, from the Chinese consulate in Thailand’s economic and commercial counsellor’s office.

“Both countries are confident the study will be completed in November,” he told reporters in Bangkok. “It was mostly the Thai side that was delaying the project … after it passes, they will have no more reasons to delay it.”

Officials from both sides earlier said construction could begin in November, but the process has been delayed because the environmental impact assessment has been waiting for approval.

The first phase of the project – stalled for months over cost, development, and labour problems – will be a 250km railway stretching from the capital Bangkok to the northeastern province of Nakhon Ratchasima.

Liang said discussions have begun for the second phase, which will extend the route to Nong Khai on the country’s border with Laos.

The rail network will ultimately be built in four sections to reach southern China.

Concerns such as technology transfers between both sides require further discussion, he said.

The massive infrastructure project falls under China’s sprawling Belt and Road Initiative, a hallmark of Chinese President Xi Jinping’s “new era” of global financial investment and development.

Lim Tai Wei, of the National University of Singapore’s East Asian Institute, said the railway project, along with similar lines planned in Malaysia and Laos, would provide the backbone of China’s transport and logistical network within the Asean Economic Community.

“They are showcases for future projects, especially for future projects in Southeast Asia,” he said.

But the railway’s critics have slammed the project as the “Train to Nowhere” for its slow start and have questioned its high costs and lack of transparency.

Thai Prime Minister Prayuth Chan-ocha, who came to power through a military coup in May 2014, was forced to use the controversial Article 44 in the constitution – allowing him to issue executive administrative orders without legal restrictions – to accelerate the project’s progress.

While Thailand does need an upgraded railway system, Sasiwan Chingchit from the Asia Foundation said the project’s lack of transparency had been a primary concern in the public debate over whether it was economically worthwhile.

“The Thai public does not look at this project positively,” she said. “If it is done properly, it would strengthen our relations in several dimensions … but it depends on how it’s done.

“For the first phase, if the two governments can deal with these transparency issues, I think people will feel more positive about the next stage.”

The project has also been delayed by bureaucratic red tape and “doubt and distrust on the Thai side about the benefits and cost effectiveness of the deal,” said Thitinan Pongsudhirak, an associate professor of political science at Chulalongkorn University in Bangkok.

He added that the railway has come to symbolise the progress of Chinese-Thai relations.

“If it does not get off the ground, it would reflect poorly on the bilateral relationship,” Pongsudhirak said.