Others worry that with the large-scale Chinese investment and China’s growing presence in the Iranian economy, Tehran will become more dependent than ever on China, already its biggest trading partner.

China is also an important market for Iranian oil, and because of remaining unilateral American sanctions that intimidate global banks, it is the only source of the large amounts of capital Iran needs to finance critical infrastructure projects. But that, apparently, is a risk the leadership is prepared to take.

“China is dominating Iran,” said Mehdi Taghavi, an economics professor at Allameh Tabataba’i University in Tehran, adding that the “Iranian authorities do not see any drawbacks to being dependent on China. Together, we are moving ahead.”

It is not just roads and rail lines that Iran is getting from China. Iran is also becoming an increasingly popular destination for Chinese entrepreneurs like Mr. Lin. With a few words of Persian, as well as low-interest loans and tax breaks from the Chinese and Iranian governments, he has built a small empire since moving to Iran in 2002. His eight factories make a wide variety of goods that find markets in Iran and in neighboring countries.

“You can say that I was even more visionary than some of our politicians,” Mr. Lin said with a laugh. Since 2013, when the “One Belt, One Road” plan was started, he has had dozens of visitors from China and multiple meetings with the Chinese ambassador in Tehran. “I was a pioneer, and they want to hear my experiences,” he said.

Mr. Lin established his factories along what will be a key part of the trade route — a 575-mile electrified rail line linking Tehran and Mashhad, financed with a $1.6 billion loan from China. When completed and attached to the wider network, the new line will enable Mr. Lin to export his goods as far as northern Europe, Poland and Russia, at much less cost than today.

“I am expecting a 50 percent increase in revenue,” Mr. Lin said. He lit another cigarette. “Of course, Iran’s economy will also grow. China will expand. Its power will grow.”