WASHINGTON -- The Obama administration on Tuesday brushed aside Iran's warning to keep U.S. aircraft carriers out of the Persian Gulf, dismissing its threats as a consequence of hard-hitting American sanctions on the Iranian economy.

Provoking a hostile start to what could prove to be a pivotal year for Iran, the country's army chief said American vessels were unwelcome in the Gulf, the strategic waterway that carries to market much of the oil pumped in the Middle East.

Iran also has warned of blocking one of the world's key tanker lanes, the Strait of Hormuz, in response to new, stronger U.S. economic penalties on Iran over its disputed nuclear enrichment program.

Iranian Gen. Ataollah Salehi's warning about the Gulf came just three days after President Barack Obama signed into law new sanctions targeting Iran's Central Bank and its ability to sell petroleum abroad.

The warnings were just Iranian saber-rattling, with no effect on U.S. plans or military movements, spokesmen in Washington said.

"It's the latest round of Iranian threats and is confirmation that Tehran is under increasing pressure for its continued failure to live up to its international obligations," White House press secretary Jay Carney said. "Iran is isolated and is seeking to divert attention from its behavior and domestic problems," he added.

Salehi didn't cite a specific vessel, but the U.S. Navy's 5th Fleet has said the aircraft carrier John C. Stennis and another vessel headed out from the Gulf and through the Strait of Hormuz last week after a visit to Dubai's Jebel Ali port.

Iran closed 10 days of naval maneuvers Tuesday, continuing a tone of military defiance but seeing the bite of international sanctions pull its currency, the rial, down to lows against the dollar earlier this week.

Pentagon spokesman George Little said the Navy operates in the Gulf in accordance with international law, maintaining "a constant state of high vigilance" to ensure the flow of sea commerce.

The 5th Fleet has long been headquartered in the Gulf state of Bahrain, serving as a key counterbalance to Iran's expanding military presence in the Gulf.