U.S. Defense Secretary Robert Gates is calling for the United Nations to place more sanctions on Iran soon.

A Pentagon spokesman told reporters Gates believes "time is of the essence" to stop Iran's pursuit of nuclear weapons.

He added that a U.N. resolution needs to come in weeks, not months.

Gate's request comes one day after Iranian President Mahmoud Ahmadinejad ordered his country's atomic agency to begin production of higher enriched uranium which can be used to make nuclear bombs.

Gates believes a resolution would lay the legal foundation necessary for nations to impose independent sanctions on Tehran and pressure the Islamic regime to scrap its nuclear program.