The floodwaters that have displaced 20 million Pakistanis and submerged nearly a fifth of Pakistan’s land are exacting a terrible toll on an already long-suffering people. That would be reason enough for the United States to be generous and compassionate in its response.

But the humanitarian interest is heightened by Pakistan’s centrality to America’s national security interests. The Obama administration must seize this chance to deepen and broaden what is already a large commitment, lest Pakistan become even more of a breeding ground for terrorism.

To be sure, the government of Pakistan is a complicated partner – whether in combating al-Qaida and the Taliban or in delivering foreign aid to its own people. Corruption is rampant, and public trust in an officialdom whose presence is barely felt in many of the affected provinces is low. Not surprisingly, Pakistan’s reputation for inefficiency and graft has deterred foreign donors in its hour of need.

The challenge for the Obama administration and other governments is to develop new mechanisms – similar to those, perhaps, that the United Nations has devised for rebuilding Haiti after its earthquake in January – that would enable relief and reconstruction with maximum transparency and honesty. If this is done successfully, the Pakistani government and its international allies, the United States included, could gain prestige in the eyes of a skeptical people. The alternative is a vacuum that extreme Islamist groups are already attempting to fill.

The American people must be there when the floodwaters recede. The moral justification is compelling enough. But the strategic rationale is real, too.