The commander of U.S. nuclear war-fighting forces says time is running out to begin modernizing nuclear weapons that are reaching the end of their useful lives.

In the words of Navy Admiral Cecil Haney, who heads U.S. Strategic Command, "we're at the brick wall stage." He says there is little room left to extend the life of weapons such as the Minuteman 3 intercontinental ballistic missile, which has been operating since 1970.

Haney spoke in an interview Friday, the day after he and other senior Pentagon leaders witnessed a Minuteman 3 test launch at Vandenberg Air Force Base in California.

Critics say the cost of nuclear modernization is too high and that the nation should reconsider whether it needs to build an entire new generation of weapons.