(Image Credit: Carolyn Kaster/AP Photo)

As tensions continue to rise over Tehran's nuclear program, President Obama today announced new sanctions against Iran's financial institutions, saying they have engaged in "deceptive practices."

"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," the president wrote in a letter to Congress.

The executive order states that all assets of the Iranian government and banks held in the United States are "blocked and may not be transferred, paid, exported, withdrawn  or otherwise dealt in." The sanctions were included as an amendment to the defense authorization bill that Obama signed into law at the end of 2011.

The move comes amid speculation of a possible Israeli attack on Iran. On Sunday, Obama stressed that diplomacy was still the "preferred solution."

"I don't think that Israel has made a decision on what they need to do. I think they, like us, believe that Iran has to stand down on its nuclear weapons program," Obama told NBC's Matt Lauer. "We have mobilized the international community in a way that is unprecedented. And they are feeling the pinch, they're feeling the pressure, but they have not taken the step that they need to, diplomatically, which is to say we will pursue peaceful nuclear power; we will not pursue a nuclear weapon. Until they do, I think Israel rightly is going to be very concerned, and we are as well."