President Barack Obama announced new U.S. sanctions on Tuesday, July 31 against foreign banks that help Iran sell its oil and said the measure would increase pressure on Tehran for failing to meet its international nuclear obligations, Reuters said.

Obama's decision, in an executive order, came ahead of congressional votes on new sanctions intended to further strip Iran of its oil-related revenues.

It also followed criticism from Republican presidential challenger Mitt Romney that the White House is failing to act strongly enough to stop Iran's suspected pursuit of a nuclear weapon. Iran says its nuclear program is for peaceful purposes.

The United States remains committed to finding a diplomatic resolution to the standoff with Tehran, but is also determined to step up the pressure, Obama said in a statement.

"If the Iranian government continues its defiance, there should be no doubt that the United States and our partners will continue to impose increasing consequences," he said.

Obama's new sanctions target foreign banks that handle transactions for Iranian oil or handle large transactions from the National Iranian Oil Company (NIOC) or Naftiran Intertrade Company (NICO), two key players in Iran's oil trade.

That builds on oil trade sanctions signed into law in December that have prompted buyers in Japan, South Korea, India and China to significantly cut their purchases to avoid penalties.

The new executive order has the same rules, providing "exceptions" to countries that have demonstrated significant cuts.