U.S. President Barack Obama signed an executive order on Monday, February 6 imposing new, stricter sanctions on Iran and its central bank, saying a broader asset freeze was necessary because Iranian banks were concealing transactions.

"I have determined that additional sanctions are warranted, particularly in light of the deceptive practices of the Central Bank of Iran and other Iranian banks to conceal transactions of sanctioned parties, the deficiencies in Iran's anti-money laundering regime and the weaknesses in its implementation, and the continuing and unacceptable risk posed to the international financial system by Iran's activities," Obama said in a letter to Congress, Reuters reported.

The executive order, described as a further step in the U.S. effort to isolate Iran, prevents any assets deemed to be in U.S. control - including foreign branches of American banks - from being transferred, paid, exported or withdrawn.