KURDPA - President Barack Obama has announced new sanctions on Iran, just as the U.S. House of Representatives and the Senate are preparing to introduce their own legislation.

President Obama has signed an executive order that imposes new sanctions on Iran's energy and petrochemical sectors to prevent the country from getting around existing sanctions.

The deputy national security adviser for strategic communications, Ben Rhodes, said the Obama administration is "sharpening the choice" for the Tehran government.

"Iran has an opportunity through diplomacy to come in line with their international obligations with respect to their nuclear program; however, we have also made it clear that if Iran fails to meet its obligations, we will steadily ratchet up the pressure," Rhodes said.

The United States and several other Western countries have united to impose sanctions on Iran, saying they are concerned that Iran's nuclear program is in reality an effort to develop nuclear weapons. Iran says that its programs to enrich uranium are solely for civilian purposes. The International Atomic Energy Agency has also voiced concern about possible military applications of Iran's nuclear program.

The U.S. Treasury Department also announced sanctions Tuesday against two financial institutions, the Bank of Kunlun in China and Elaf Islamic Bank in Iraq, for facilitating transactions for Iranian banks that are already subject to international sanctions.

"Today's action exposes these banks' continued business with designated Iranian banks, and effectively cuts them off from the U.S. financial system," said David Cohen, the under secretary for terrorism and financial intelligence with the U.S. Treasury Department.

Cohen said the banks had been helping Tehran to finance its nuclear program and international terrorism.

Senior Obama administration officials rejected suggestions that the international sanctions against Iran are not having a real impact on that country's nuclear program. National Security official Ben Rhodes says the impact is significant, and will continue to be felt even more severely in Tehran over the coming weeks.

"Frankly, several years ago it was the international community that was divided about how to deal with Iran, whereas the Iranian leadership was very united. What we see today is not just a unified international community, but you see sharp divisions within the Iranian political system," he said.

The White House sanctions come just as both houses of Congress work to introduce their own sanctions against Iran this week before leaving for a five-week recess. Some lawmakers have grown impatient and criticized President Obama for not being tough enough on Iran's nuclear ambitions.