Iran and Pakistan have inaugurated a controversial gas pipeline project. Regional powers like Saudi Arabia, the United Arab Emirates and Qatar have reportedly expressed their displeasure through diplomatic envoys. However, perhaps most worrying for Pakistan is the reaction of the US government, which has repeatedly warned against going ahead with the pipeline. Washington has said that the project could expose Pakistan to economic penalties under the Iran Sanctions Act. Al Jazeera's Imtiaz Tyab reports from Karachi in Pakistan.