From Reuters :
A U.S. Republican lawmaker on Tuesday blocked Democrats from passing legislation designed to further punish Iran  for developing its nuclear program, and each side blamed the other for its failure in a presidential election year that will put extra scrutiny on President Barack Obama to be tough on Tehran.
The legislation, which had the backing of many Democratic and Republican Senators, focused on foreign banks that handle transactions for Iran's national oil and tanker companies, and included a host of measures aimed to close loopholes in existing sanctions.
A handful of Republicans wanted to include additional measures to the bill such as sanctions on companies that insure trade with Iran. But Majority Leader Harry Reid wanted to take up the legislation without amendments.
"New changes to the bill at this time will only slow down its passage," Reid, a Democrat, said before he sought unanimous consent from Senators to approve the legislation - a procedure that allows no amendments.
Senator Rand Paul formally objected to taking up the legislation unless the Senate would also consider his amendment to it saying that nothing in the bill could be construed as an authorization of war against Iran or Syria . This effectively blocked the bill from advancing.
The timing of the next step was not immediately clear.
The latest set of penalties signed into law by President Barack Obama in December have made it increasingly difficult for Tehran to sell its oil. They are aimed at slowing Iran's nuclear program, which Tehran has said is purely for civilian purposes. The United States and some other Western countries say the program is for nuclear weapons.
The bill would have built on efforts by the United States and other Western nations to implement oil and banking sanctions.
"These sanctions are a key tool as we work to stop (Iran) from obtaining a nuclear weapon, threatening Israel and ultimately jeopardizing U.S. national security," Reid said earlier on Tuesday.
The Senate Banking Committee easily passed the sanctions bill on February 2 and the full House of Representatives passed its version in December.
Since then, several lawmakers have floated additional proposals to penalize underwriters that insure oil and gas trade with Iran; to block foreign companies dealing with Iranian energy companies from U.S. financial markets; and to ban foreign companies that buy Iranian oil from buying oil from U.S. emergency reserves.
Before Paul blocked the bill, Reid said Democratic senators had agreed to move forward without offering any amendments, which could speed a vote. "I'm willing to move this bill without amendments at any time," Reid said afterward.
Democrats were quick to blame Republicans for blocking the bill. "I hope that the select few Republicans who reportedly blocked this important bill will reconsider their opposition and allow it to move forward as soon as possible," said Tim Johnson, the Democratic chairman of the Senate Banking Committee.