WASHINGTON, March 28 (Reuters) - The United States has told Russia it will cease exchanging some data on its nuclear forces following Moscow's refusal to do so, the White House said on Tuesday (Mar 28), calling this a response to Russia's suspending participation in the New START nuclear arms treaty.

While Russian President Vladimir Putin has not formally withdrawn from the treaty, which limits the two sides' deployed strategic nuclear arsenals, his Feb 21 suspension imperils the last pillar of US-Russian arms control.

Between the two of them, the United States and Russia hold nearly 90 per cent of the world's nuclear warheads - enough to destroy the planet many times over.

"Under international law, the United States has the right to respond to Russia's breaches of the New START Treaty by taking proportionate and reversible countermeasures in order to induce Russia to return to compliance with its obligations," a spokesperson for the National Security Council said.

"That means that because Russia's claimed suspension of the New START Treaty is legally invalid, the US is legally permitted to withhold our biannual data update in response to Russia's breaches," the spokesperson added.

"Russia has not been in full compliance and refused to share data which we ... agreed in New START to share biannually," John Kirby, the National Security Council Coordinator for Strategic Communications, told reporters in a conference call.

"Since they have refused to be in compliance ... we have decided to likewise not share that data," he added. "We would prefer to be able to do (this) but it requires them being willing to as well."

Signed in 2010 and due to expire in 2026, the New START treaty caps the number of strategic nuclear warheads that the countries can deploy. Under its terms, Moscow and Washington may deploy no more than 1,550 strategic nuclear warheads and 700 land- and submarine-based missiles and bombers to deliver them.

Under the treaty's "Biannual Data Exchanges," each provides a declaration of deployed strategic delivery vehicles, launchers and warheads, including a breakdown of warhead numbers deployed across the three types of delivery vehicles - air, sea and land-based.

Each also breaks down how many strategic delivery vehicles and warheads are deployed at each declared base.

A State Department spokesperson said that "aside from the biannual data exchange, the United States continues to provide all required notifications under the New START Treaty."