Pakistan suffers from energy under-supply. A pipeline contract, supplying Pakistan with Iranian natural gas, would help Pakistanis big time if enacted.

However, the US government prefers the principle of enacting sanctions against Iran to a humanitarian development project like this pipeline.

Clinton warned that if Pakistan proceeds with the pipeline project, it will be subject to the punitive measures of the Iran Sanctions Act...

Pakistan’s determination to continue with the pipeline project stems from its desperate need for foreign energy. Pakistan has been plagued by a deepening energy crisis in recent years that has crippled industry and made life increasingly unbearable for the masses.

Last month, unplanned power outages lasting up to 10 hours forced businesses to shut down across much of the country. The frequent power-outages have led factory owners in Karachi and other industrial centers to halt production and lay off hundreds of thousands of workers. Powers cuts have provoked spontaneous protests in every province over the past year, to which the Pakistani police have repeatedly responded with deadly force.

www.wsws.org/articles/2012/mar2012/pair-...

Needless to say perhaps, there also are voices who see the rails to Auschwitz being rebuilt:

ILF Consulting Engineers, a German-Austrian company, confirmed on Monday that it is providing “advice and planning” work in the technological development of an Iranian-Pakistan pipeline project...

Austria and Germany are considered by experts in Europe to be the weakest links in the enforcement of the sanctions regime targeting Iran. Germany remains Iran’s most important EU trade partner, with an annual bilateral trade of roughly 4 billion euros.

www.jpost.com/International/Article.aspx...

Must Pakistan suffer from the Iran embargo? If so, why?

This is part of the colonialist strategy of the US and Western powers to control the energy resources of that part of the world.   Anyone who dares not to go along with the policy is confronted  with the whole force  of the Western powers.  War is just one means at their disposal.  Ask  Iraq, Afghanistan, Lybia and soon Iran. 

 That is why the US reserves the right  to decide whether those people can build a pipeline or not. "Development" is not something colonialism is concerned with. A backward  place  is easier to control.

Not to mention being able to pipe oil directly to China over land.