"They're buying them because they're cheap. The underlying motive behind buying these mills is making money, not enhancing the political glory of Russia," said Tim McCutcheon, a partner and fund manager at DBM Capital Partners in Moscow.

Betting on U.S. steel is risky, analysts say, as the once-mighty automotive and construction sectors are in decline and demand growth has been eclipsed by emerging economies such as China and India.

But this has not deterred Alexei Mordashov, owner of Severstal, whose acquisitions have pushed his company into the top five steelmakers in the United States -- a scenario unthinkable when the countries were Cold War enemies.

"We remain committed to growth in North America and believe in the long-term promise of the U.S. market," Mordashov, ranked the world's 18th-richest man by Forbes magazine, said last month after announcing Severstal's latest acquisition.

Mordashov says the weak dollar is making Russian companies, which derive most of their revenues supplying a domestic market expanding at more than 7 percent annually, more competitive in the United States. The dollar has lost nearly 15 percent of its value against the ruble in the last two years.

The country's foray into North American steel marks the growing power of its leading steel firms, which are unburdened by high raw material costs after absorbing their own mines during a carve-up of the country's mineral assets in the late 1990s.

Severstal was the first Russian company to buy a U.S. steel asset when it bought Dearborn, Michigan-based Rouge Steel, once the in-house steel unit for Ford Motor, in late 2003.

Evraz Group, part-owned by billionaire Roman Abramovich, followed with the acquisition of Oregon Steel Mills and Claymont Steel Holdings. Last month it also agreed to buy IPSCO's North American assets from Sweden's SSAB.

Steel barons have avoided the political scrutiny that has hampered other Russian attempts to invest overseas by spending at a time when parts of the U.S. steel industry are on their knees and limiting their ambitions to small or midsized mills.

This has, however, raised questions over asset quality.

Charles Bradford, New York-based metals analyst for Soleil Securities Group, said Russians had bought assets nobody else wanted and face a huge challenge in turning them round.

"Some of these plants were so bad. I don't know if they could have been sold as scrap," he said.

But outdated mills shunned by U.S. firms present less fear to those well acquainted with the overmanned behemoths that once served the Soviet military-industrial complex.

"Someone who comes from Cherepovets or Lipetsk is not going to have a problem with an integrated mill," DBM Capital's McCutcheon said, referring to the home cities of Severstal and NLMK.