An official with the US Department of Defense on Wednesday denied media reports that a Russian nuclear-powered submarine recently operated in restricted US waters for up to a month without being detected.



"I don't know what that information was based on, but it was not correct," Wendy Snyder, a spokeswoman with the Pentagon, said to the Global Times.



The Washington Free Beacon newspaper, citing unnamed sources, had reported that a Russian nuclear attack submarine sailed undetected in the Gulf of Mexico for weeks and was not discovered until it had left the strategic waters.



"The stealth underwater incursion in the Gulf took place at the same time Russian strategic bombers made incursions into restricted US airspace near Alaska and California in June and July, and highlights a growing military assertiveness by Moscow," the report said



A Russian attack submarine also sailed close to the shores in 2009, it added.



The report said the Russian submarine was of the Akula class, an attack warship capable of carrying long-range ballistic missiles and was developed to counter the US navy's Los Angeles class subs.



Russia's Interfax News Agency said the Akula differs from older submarines due to its greater stealth capabilities and that it is already the main submarine class employed by the Russian fleet.



"Sending a nuclear-propelled submarine into the Gulf of Mexico-Caribbean region is another manifestation of President (Vladimir) Putin demonstrating that Russia is still a player on the world's political-military stage," Normal Polmar, a naval analyst and submarine warfare specialist, told the newspaper.



There have been no comments from Moscow on the reports as yet.



The reports of the Russian submarine's appearance in US strategic waters came against the backdrop that US President Barack Obama plans to slash $487 billion in the US defense budget over the next 10 years.



The plan has raised questions in the US about whether the country will be able to maintain its military advantage over other nations in the future.