The US government is reviewing whether Russia has broken a nuclear arms control treaty, and has warned its Nato allies of Russia’s alleged testing of a new cruise missile.

State department spokeswoman Jen Psaki told reporters on Thursday US officials do not yet regard the treaty in question, which was part of a series of agreements that helped bring an end to the Cold War, to be in serious jeopardy, but are examining what they claim is clear evidence of the missile's use.

The possibility of Russia having violated the 1987 treaty – the Intermediate-Range Nuclear Forces Treaty, a deal agreed by Ronald Reagan and Mikhail Gorbachev – is likely to complicate current attempts by President Barack Obama to convince Congress of the need for further reductions in the US stockpile of arms.

Psaki confirmed that under secretary of state Rose Gottemoeller had shared American fears about tests of the missile – which are said to date back to 2008 – at a recent Nato conference in Europe, but she stressed that a formal decision on whether to declare a violation had not yet been made.

“We take questions about arms-control treaties very seriously,” said Psaki. ”When compliance questions arise, we work to resolve them with our treaty partners.”

An official US report detailing treaty issues for 2013 is due later this year, and officials are currently considering further action, according to the State Department.

“It's an intensive interagency review process,” added Psaki. “As part of that we consult with our treaty partners and allies and there hasn't been an outcome of that process, nor would I want to make a prediction of what the conclusion would be.”

The New York Times reported that fears over the new cruise missile were separate from concerns over a separate Russian two-stage missile, the RS-26, which US officials regard as a circumvention, rather than a breach, of the medium-range ban. It is also capable of long-range flights.