In an incident that recalls the days of the Cold War, two nuclear-powered Russian attack submarines have been patrolling international waters off the U.S. East Coast, the Associated Press reports. Although the submarines have yet to do anything to provoke American forces, two senior U.S. officials did acknowledge their presence. This latest incident comes at a time of increased tension between the U.S. and Russia. The Obama administration is seeking to start a missile-defense plan in Central Europe. The Russians conducted military exercises in the Caribbean last year. Officials said they were not informed by Moscow of the submarines' presence.