Rose Gottemoeller

The treaty is called New START, and it went into force 15 years ago.

Rose Gottemoeller negotiated New START with the Russians.

She says it was the latest in a decades-long effort to reduce the number of nuclear weapons each side deploys.

But the treaty can't be renewed, and any hope for a follow-up treaty ended with Russia's invasion of Ukraine.

Russian President Vladimir Putin has offered a one-year informal extension to New START's limits, and Gottemoeller thinks President Trump should take him up on it.

Otherwise, we're into the depths of a nuclear arms race, and that's an expensive proposition.

New start expires at midnight.

Jeff Brumfield, NPR News.