U.S. Senate Republicans said they needed more time to examine a revised packaged of new economic sanctions on Iran's oil sector and make sure that it was tough enough.
The move angered Senate Democrats, who had expected a unanimous Senate vote of approval ahead of the May 23 talks in Baghdad between Iran and world powers.
The proposed sanctions would close loopholes in sanctions laws and look to further limit Iranian oil and tanker activities, as well as impose additional penalties on financial institutions and satellite companies involved in sanctionable activities.
Senate Majority Leader Harry Reid was quoted as saying that Iranian officials must be laughing at the U.S. Congress over the political disagreements.
Iran is facing sanctions over its disputed nuclear activities.
Based on reporting by Reuters and "Jerusalem Post"