The reason for the slow progress from the Russian side regarding a border-crossing bridge over the Heilongjiang River (the Amur River) at Tongjiang, Northeast China's Heilongjiang Province, is not a technical one, an insider told the Global Times Sunday.

The structure is the first railway bridge to cross a river and link China with Russia, according to media reports.

The reason that the slow progress cannot be for technical problems is because the design of the bridge was based heavily on advice from Russian experts, said the insider, who declined to be identified.

The Tongjiang-Nizhneleninskoye Railway Bridge is a joint project of China and Russia. It has a designed annual shipment volume of 21 million tons. The Chinese side is responsible for the construction of about 1,900 meters of the bridge and the Russian side for about 330 meters.

According to a statement from China's Ministry of Commerce on July 12, the principal part of the bridge built by the Chinese side has been completed, after construction formally began in June 2014. The Chinese section cost about 2.58 billion yuan ($386 million).

On the Russian side, construction workers and equipment have entered the site to begin preparation, the same statement said, noting that the Russian section is expected to be completed within two years, costing about 9 billion rubles ($142 million).

The bridge will reduce the cost of transporting iron ore excavated in Russia to China, shortening the journey to a major Chinese steel mill to just 233 kilometers from 1,040 kilometers at present, according to a New York Times report published on Saturday.

"Earlier this month, representatives from Nizhneleninskoye, some design institute in Russia, Russian Railways and Rubicon, a company supervising the project, visited government officials in Tongjiang," the insider said.

The Russians are probably still in the design phase, the insider said.

"We have spotted one crane, one shovel and some plank houses, and it looks like they are starting the project, but nothing major is happening on the site," the insider said, giving a firsthand account of progress on the project.

The two sides discussed building the bridge for about a decade, but work did not really begin until 2014, noted the insider.

The design took so much advice from Russian experts that there cannot be any technical problems blocking construction, according to the insider.

If the bridge is completed, it will have significance in boosting connectivity between Heilongjiang and Russia, the insider said, adding that the design allows freight trains carrying iron ore, crude and natural gas, and even a few passenger trains, to pass.

"I suspect that the economic slowdown in Russia caused some of the delay on the Russian side. And there are also some Russians who believe that resources should not be sold China," the insider said.