TEHRAN, March 13 (Reuters) - President Mahmoud Ahmadinejad dismissed international sanctions against Iran as a “childish idea” on Friday as he officially launched a natural gas project in the Gulf, Iranian media reported.

The comments came a day after U.S. President Barack Obama said he was extending economic sanctions against Tehran as it continued to pose an “extraordinary threat” to the national security, foreign policy and economy of the United States.

Obama declared the routine extension of punitive measures imposed by former U.S. President Bill Clinton in 1995 in a public notice on Thursday.

Ahmadinejad said the idea of creating obstacles for Iran’s development with sanctions was “a childish idea and a big mistake,” the official IRNA news agency reported. (Reporting by Hashem Kalantari; Writing by Fredrik Dahl)