With friends like these, who needs enemies? This question has undoubtedly been on the minds of Pentagon officials and members of Congress who are grappling with the issue of additional economic and military assistance to Pakistan, a critical ally in the seemingly never-ending war against the Taliban and al-Qaida (both homegrown and in neighboring Afghanistan), amid reports that the Pakistani military is illegally modifying previously provided U.S. defensive missiles for offensive purposes.

Making matters considerably worse is that the same question has been on the minds of Pakistan's military and political leaders for years. They have been long convinced — not entirely without justification — that the U.S. is an unreliable partner and fickle friend that is only there when it suits Washington's purpose, one that would prefer a long-term strategic relationship with its archrival India, rather than with Islamabad.

Defense Secretary Robert Gates acknowledged this lack of confidence during an interview with the al-Jazeera television network last week: "As soon as the Soviets left Afghanistan, we turned our backs on Afghanistan and we did not cultivate our relationship with the Pakistanis properly." This was "a serious strategic mistake," Gates admitted, as it sparked doubts about America's commitment to the region. But, he told his al-Jazeera audience, "I believe we've learned our lesson," vowing that today, "Pakistan can count on us for the long term." But can we count on Pakistan?

The arms modification issue is just the tip of the iceberg when it comes to the growing mutual crisis of confidence between Washington and Islamabad, but it is symptomatic of deeper problems of mistrust. According to a recent New York Times article, the Pentagon has accused Pakistan of secretly altering U.S. Harpoon defensive anti-ship missiles for offensive use against land-based targets. Pakistan was also accused of modifying several U.S.-provided P-3C Orion surveillance aircraft for land attack. The U.S. Arms Control Export Act under which such arms deliveries are governed specifically prohibits such alterations.

If true — and Pentagon officials seem convinced that it is, even though some experts are skeptical (and, not surprisingly, the Pakistani government has vehemently denied the accusations) — this would enable Pakistan's small navy and naval air arm to strike Indian land targets, complementing the sizable land-based missile arsenal that Islamabad has developed and complicating New Delhi's defensive requirements. The Obama administration's biggest fear is that this could put at risk future economic and military assistance planned for Pakistan and, for that matter, ironically could impact future arms sales to India as well, due to concerns about spurring a destabilizing arms race between the two South Asia rivals.

The Pentagon has been trying, with only modest success, to get the Pakistani military to focus its efforts on confronting the Taliban and al-Qaida inside Pakistan and especially along its northeast border with Afghanistan, while the Pakistani military has remained fixated on historical rival India, despite increasing internal instability. While Washington believes it can and must have good relations with both Islamabad and New Delhi, the two continue to look at one another and at the other's relationship with the U.S. in "win-lose" terms.

There is an ominous nuclear dimension to Washington's concerns. Many of Pakistan's nuclear facilities were placed in the western and northern regions of the country out of fear of an Indian invasion. These areas are now populated with Taliban and al-Qaida insurgents and, in recent years, at least three facilities suspected to be part of Pakistan's nuclear complex have come under attack by militants, including an August 2008 incident at the Wah cantonment, widely understood to be one of Pakistan's main nuclear weapons assembly sites. Pentagon officials are constantly (and rightfully) seeking reassurance from Islamabad over the security of its nuclear arsenal, but the Pakistani military has been reluctant to cooperate, presumably out of fears that the real U.S. intention is not nuclear safety but a desire to neuter Pakistan's nuclear weapons capability.

Concerns about Pakistan's trustworthiness as a security partner and doubts about the security of its nuclear arsenal and its commitment to focus on the Taliban/al-Qaida threat could put in jeopardy the Obama administration's proposal to provide Pakistan with $7.5 billion in largely civilian aid over the next five years, while a failure to provide such support will reinforce Pakistan's paranoia about America's reliability and commitment.

Congress needs to approve the aid and reconstruction package, but Islamabad also needs to provide reassurance to Washington about its own reliability.

Ralph A. Cossa is president of the Pacific Forum CSIS (www.pacforum.org), a Honolulu-based nonprofit foreign policy research institute. He wrote this commentary for The Advertiser.