Senator Ed Markey’s bill to limit the authority of the president — any president — to use nuclear weapons first in a conflict is an important step toward changing a dangerous policy (“Markey wants to curb Trump’s power to launch nuclear weapons,’’ Jan. 24).

Despite the vast superiority of its conventional forces, the United States reserves the right to use nuclear weapons first in a wide array of circumstances and has detailed plans for doing so.

Even worse, the US president has the authority to decide — on his or her own, for whatever reason — to launch nuclear weapons.

Markey’s bill is an important step, since it requires Congress to be involved in the momentous decision to launch a first strike, a decision that would have disastrous consequences. But the United States should go beyond that and declare that the sole purpose of its nuclear weapons is to deter and, if necessary, respond to the use of nuclear weapons by another country.

US nuclear use policies must be changed, no matter who is sitting in the Oval Office.

Lisbeth Gronlund

Codirector and senior scientist, Global Security Program

Union of Concerned Scientists

Cambridge