A report in a major U.S. newspaper says Washington has accused Pakistan of illegally modifying U.S.-made missiles to make them capable of striking land targets, a potential threat to India.
The New York Times says the charge was made in an unpublicized diplomatic protest in late June to Prime Minister Yusuf Raza Gilani and other top Pakistani officials.
The newspaper reports U.S. officials suspect Pakistan has modified the missiles in a manner that violates the Arms Control Export Act.
The Times says Pakistan has denied the charges, saying it developed the missile on its own.
The missile dispute is flaring up as the Obama administration seeks congressional approval for $7.5 billion in aid for Pakistan over the next five years.
The New York Times says U.S. intelligence detected a suspicious missile test on April 23 that was never announced by Pakistan and appeared to give Pakistan a new offensive weapon.
At issue are Harpoon anti-ship missiles sold to Pakistan during the administration of U.S. President Ronald Reagan as defensive weapons during the Cold War in the 1980s.
The newspaper report says there is "growing concern" in the Obama administration about the speed with which Pakistan is developing new generations of both conventional and nuclear weapons.
The Times spoke to a U.S. official who said there is a "concerted effort" to get Pakistan to slow down its development of weapons.
Some information for this report was provided by AFP and Reuters.