For a country that is not exactly on solid ground, maybe increasing the number of nuclear weapons Pakistan has is not such a good idea.  From the New York Times:

Members of Congress have been told in confidential briefings that Pakistan is rapidly adding to its nuclear arsenal even while racked by insurgency, raising questions on Capitol Hill about whether billions of dollars in proposed military aid might be diverted to Pakistan’s nuclear program.

[...]

Inside the Obama administration, some officials say, Pakistan’s drive to spend heavily on new nuclear arms has been a source of growing concern, because the country is producing more nuclear material at a time when Washington is increasingly focused on trying to assure the security of an arsenal of 80 to 100 weapons so that they will never fall into the hands of Islamic insurgents.

The administration’s effort is complicated by the fact that Pakistan is producing an unknown amount of new bomb-grade uranium and, once a series of new reactors is completed, bomb-grade plutonium for a new generation of weapons. President Obama has called for passage of a treaty that would stop all nations from producing more fissile material — the hardest part of making a nuclear weapon — but so far has said nothing in public about Pakistan’s activities.

Obama administration officials said that they had communicated to Congress that their intent was to assure that military aid to Pakistan was directed toward counterterrorism and not diverted. But Admiral Mullen’s public confirmation that the arsenal is increasing — a view widely held in both classified and unclassified analyses — seems certain to aggravate Congress’s discomfort.

Whether that discomfort might result in a delay or reduction in aid to Pakistan is still unclear.

The Congressional briefings have taken place in recent weeks as Pakistan has descended into further chaos and as Congress has considered proposals to spend $3 billion over the next five years to train and equip Pakistan’s military for counterinsurgency warfare. That aid would come on top of $7.5 billion in civilian assistance.

The US is going to give Pakistan billions of dollars without any real way to make sure they do not use the money for more nukes.  Then, once they have more nukes there is no guarantee the official government will not collapse because of all of the strife.  This in turn could lead to the Taliban getting their hands on nuclear weapons.  That of course is a worst case scenario, however Pakistan is certainly not in the best shape right now.