Tough new US sanctions targeting Iran’s central bank and financial sector over its controversial nuclear program are "unjustifiable."

Tough new US sanctions targeting Iran's central bank and financial sector over its controversial nuclear program are "unjustifiable," a top Iranian official said Sunday.

Iran will opt to "find an alternative to meet its demands" just as it managed to counter previous sanctions "which have failed to halt Iran's trade," Mohammad Nahavandian, the head of Iran's chamber of commerce, told the ISNA news agency.

The new US measures, signed into law Saturday by President Barack Obama, were "definitely unprecedented and unjustifiable" and would lead to "reciprocal losses," he said.

"Although sanctions have raised the cost of Iran's trade, they have failed in their political objectives of altering the political will of Iranians" in pursuing their nuclear goals, Nahavandian said.

The sanctions, meant to punish Iran for its nuclear program, were contained in a mammoth $662-billion US defense bill. Obama signed them into law despite reservations they would ties his hands on setting foreign policy.

Iranian leaders and military officials have warned such sanctions could push them to close the strategic Strait of Hormuz at the entrance to the Gulf.

Twenty percent of the world's oil passes through the strait, making it the "most important chokepoint" globally, according to the US Energy Information Administration.

Iran's navy forces are currently conducting a 10-day war games near the strait.