Russia on Friday formally designated the United States and the Czech Republic as "unfriendly states" amid the biggest crisis in ties between Moscow and Washington in years.

The Russian government released a decree signed by Prime Minister Mikhail Mishustin that was accompanied by a list of "unfriendly states" that "have carried out unfriendly actions" against Russia, Russian nationals or Russian entities.

The list now includes the US and the Czech Republic.

The Czech embassy will be allowed to employ no more than 19 Russian nationals and the US embassy none at all, Moscow said.

Kremlin spokesman Dmitry Peskov said on Friday that Moscow remained ready for dialogue, state news agency TASS reported, stressing the fact that Russia had now only two nations on its "unfriendly states" list.

Prague said the step would only "escalate relations" between Moscow and the Czech Republic, the EU and its allies.

"We are sorry that Russia has embarked on the confrontation road to its own detriment," the Czech foreign ministry said in a statement.

"This measure will also indirectly affect the potential development of relations between ordinary citizens, tourism, and the development of business relations," it added.

EU chief Charles Michel tweeted the bloc's "full solidarity" with Prague as he insisted the move "undermines diplomatic relations".

"Efforts to divide the EU are in vain," Michel wrote.

Russian President Vladimir Putin's relations with the US have suffered since Joe Biden took over as president from Donald Trump
Russian President Vladimir Putin's relations with the US have suffered since Joe Biden took over as president from Donald Trump AFP / Kirill KUDRYAVTSEV

In recent months tensions have spiralled between Russia and the West over a litany of issues, including Russia's troop build-up on Ukraine's border, interference in US elections and other perceived hostile activities.

Russia-US relations have rapidly deteriorated after US President Joe Biden increased pressure on the Kremlin since becoming US president in January.

Washington in April announced sanctions and the expulsion of 10 Russian diplomats in retaliation for what it says is interference by the Kremlin in US elections, a massive cyber attack and other hostile activity.

Russia in response expelled 10 US diplomats, banned top US officials from entering the country and prohibited the US embassy from employing foreign nationals.

After Biden likened Russian President Vladimir Putin to a "killer," Russia temporarily recalled its ambassador from the United States and later said the US envoy should also head to Washington for consultations.

The US embassy in Moscow was forced to suspend most consular services to its nationals and stopped issuing visas due to a drastic reduction of its staff following the tit-for-tat sanctions.

But on Friday it said it would temporarily resume consular services for its citizens "through July 16."

Tensions have also spiralled with the Czech Republic after Prague accused Russian military intelligence of being behind a deadly explosion at an ammunition depot in eastern Czech Republic in 2014.

Moscow said last month it would cap the number of the Czech embassy staff in a tit-for-tat move after the EU country announced it was expelling dozens of Russian diplomats.