The import of gas from Iran has been part of a long running project, called The Peace Pipeline, to build a pipeline from Iran to go through Pakistan first and then India to deliver gas to both countries. In 1995 Pakistan and Iran signed a preliminary agreement. Due to U.S. pressure against it, this deal was not finalized until June 2010.
Iran and India signed an agreement in 1999, but, due to pressure from Washington, India never finalized the deal.
Even when Pakistan did sign on, it never gave the order to start work on the construction of the pipeline from its border to import Iran's gas, until July 6th this year. Two major factors seem to have pushed the Pakistanis over the start line. One is the ensuing energy crisis at home. The other is that the competitor to the Peace Pipeline, the Trans Afghanistan Pipeline, is considered to be too risky as the main source of Pakistan's energy, since it runs through Taliban territory in Afghanistan.
It's possible that this, as well as the expulsion of U.S. trainers, was partly responsible for the U.S. decision to suspend part of its military aid to Pakistan. But, whether or not the two events are explicitly linked, the current rift with Washington has made it easier for Pakistan to ignore U.S. pressure and pursue the Peace Pipeline deal with Iran.
Not only have the Iranians secured Pakistan as a client, they know Pakistan's dire need for Iranian gas means they will not be leaving Iran's side anytime soon. Some analysts have estimated that gas from Iran provide at least 20 percent of Pakistan's energy needs. Others have suggested 50 percent.
The question that must now be asked is, how far will the Pakistan-Iran rapprochement go?
In all likelihood, not very far.
Aside from this recent victory, the most that Iranians can look forward to is the possibility of closer security cooperation with the Pakistanis against the remnants of the Jundollah terrorist organization, an ethnic Baloch group that spans both countries.
When it comes to Iran's nuclear program and its influence in the Middle East, Tehran is unlikely to find Pakistan of much help.
As new Wikileaks reports indicate, despite the help of Pakistani nuclear scientist A.Q Khan in building Iran's post-revolution nuclear program, some top Pakistani officials do not want Iran to become a nuclear armed power. The Pakistani leadership, wishing for their country to remain the only nuclear Islamic state, cooperated with George W. Bush's efforts against Iranian nuclear development.
This is unlikely to change anytime soon. Pakistan, for all its rapprochement with Iran, considers it to be a rival in Afghanistan.
There is also the question of Saudi Arabia. Islamabad has very close relations with Riyadh. In Washington arms control and Middle East policy analyst circles, it has long been speculated that, should Iran become a nuclear power, Pakistan would be obliged to provide a nuclear umbrella to protect Saudi Arabia, which financed part of Pakistan's nuclear program. But this is only a theory, of course. What's not a theory is the fact that Saudi Arabia and Pakistan have close economic and political relations that are far more extensive and important to Pakistan than anything Iran could offer. In the ensuing cold war between Iran and Saudi Arabia, Pakistan is unlikely to leave the Saudi side.