The suggestion that Russia violated its treaty obligations by deploying a land-based cruise missile is also a complicated matter, officials and private analysts told NBC News.
The U.S. has long been aware that the Russians have been preparing new cruise missiles.
Starting in 2014, the Obama administration flagged a new Russian cruise missile under development as a violation of INF Treaty. President Obama sent a letter to Vladimir Putin about the alleged breach.
The new missile, designated SSC-X-8, was first flown in September 2015, and the U.S. condemned the tests.
In November 2016, the two sides met under the INF verification framework in Geneva, but there was no agreement. Moscow then deployed the weapon, now referred to as the SSC-8, the elimination of the "X" designating it as operational.
One defense official told NBC News that the Russians have assigned the system to a unit based inside Russia. So while it is now believed to be operational, it has not left the country.
The U.S. maintains the missile is a violation. Dmitry Peskov, spokesman for Putin, said the U.S. has not made a formal complaint.
Hans Kristensen, director of the Nuclear Information Project at the Federation of American Scientists, said the question is not settled. "Whether the missile is operational, what variant it is, and how it might violate the INF Treaty is still wide open to debate."
Kristensen said the deployment could be seen as a Russian response to the U.S. deployment of new conventionally-armed Joint Air to Surface Missile (JASSM), which the Kremlin sees as a potential provocation. The U.S. has deployed the new missile on its own strategic bombers, some missiles are already deployed in Germany, and more are being sold to the Polish and Finnish air forces.