Techsnabexport, the Russian state company that exports low-enriched uranium, is expected to sign the contract in Moscow with a consortium of American nuclear companies. Techsnabexport declined to identify its American partners or the size of the contract on Monday.

The new contract is separate from a program to dilute surplus weapons uranium into civilian fuel for use in American reactors. Under that so-called megatons to megawatts program, begun in 1993, Russia is already the largest supplier of enriched uranium to American utilities and provides about half of all uranium consumed in civilian reactors in the United States.

Yet Russia has been prohibited from selling directly to the utilities by provisions of American law to prevent dumping at below-market prices, and it was compelled to deal only through a monopoly importer, the United States Enrichment Corporation.

That company was originally part of the United States Department of Energy, and the megaton-to-megawatts deal was a government-to-government agreement. When the United States sold off the enrichment corporation to a private company, the new entity was given a continuing monopoly on the sale of blended-down warhead materials from Russia. The company, USEC, said it paid competitive prices for the material. The Russians, meanwhile, complained that they were being underpaid.

In a negotiated settlement in February 2008, the United States agreed to allow Russia to sell low-enriched uranium directly to domestic utilities without the involvement of the enrichment corporation. But all sales of diluted weapons uranium will still go through the corporation. A spokeswoman for the company said the initial direct Russian sales will be small and will not harm its business.

Nuclear reactors run on uranium that is composed of 3 to 5 percent uranium 235. In nature, uranium is only 0.7 percent uranium 235.

Uranium used in weapons and in the reactors that power nuclear submarines use more than 90 percent uranium 235. “Enrichment” means raising the proportion of 235 compared with the dominant type, 238, and the Russian industry was set up to provide large volumes of high-enriched uranium for weapons and marine reactors.

Russia is a major supplier to the developing world by tapping this cold war-era military industrial base. It has provided 80 tons of low-enriched uranium manufactured into fuel assemblies to Iran for use in that country’s Bushehr reactor, for a price of $46 million, according to Atomstroyexport, the Russian contractor building the reactor.