WASHINGTON — Gen. James E. Cartwright, the retired vice chairman of the Joint Chiefs of Staff and a former commander of the United States’ nuclear forces, is adding his voice to those who are calling for a drastic reduction in the number of nuclear warheads below the levels set by agreements with Russia.

General Cartwright said that the United States’ nuclear deterrence could be guaranteed with a total arsenal of 900 warheads, and with only half of them deployed at any one time. Even those in the field would be taken off hair triggers, requiring 24 to 72 hours for launching, to reduce the chance of accidental war.

That arsenal would be a significant cut from the current agreement to limit Russia and the United States to 1,550 deployed warheads each, down from 2,200, within six years. Under the New Start agreement, thousands more warheads can be kept in storage as a backup force, and the restrictions do not apply to hundreds of short-range nuclear weapons in the American and Russian arsenals.

“The world has changed, but the current arsenal carries the baggage of the cold war,” General Cartwright said in an interview. “There is the baggage of significant numbers in reserve. There is the baggage of a nuclear stockpile beyond our needs. What is it we’re really trying to deter? Our current arsenal does not address the threats of the 21st century.”