The White House's messaging is intentionally hazy to make the Kremlin uneasy about the worst-case option, the outlet has reported

The United States has been privately warning Russia of grave consequences should Moscow resort to nuclear weapons in the Ukraine conflict, the Washington Post reported on Thursday. According to US officials cited by the outlet, the administration of US President Joe Biden, however, has opted to keep its message on the matter deliberately vague.

The Post's sources noted that communication with Moscow on the nuclear issue has been ongoing in recent months. While US officials declined to say who has delivered the messages and what exactly they were about, the vagueness is reportedly intended to cultivate "strategic ambiguity" and leave the Kremlin guessing about how the US would respond should Russia deploy nukes.

Meanwhile, the outlet notes that it is also unclear if Washington had been in contact with Moscow since Wednesday, when Russian President Vladimir Putin announced a partial military mobilization and pledged to use "all means" necessary to defend the country's territorial integrity in the face of external threats.

However, US officials indicated that there were no signs that Russia was moving its nuclear assets to prepare for a nuclear strike, according to the Washington Post.

On Thursday, Dmitry Medvedev, Russia's former president, said that Moscow could use nuclear weapons to defend its territory, including the Donbass republics and Zaporozhye and Kherson Regions, should they decide to join Russia.

The report about Washington's nuclear warnings comes after last week US President Joe Biden warned Russia that should it use weapons of mass destruction in Ukraine, it would face harsh consequences and become a global "pariah."

In mid-August, however, Russian Defense Minister Sergey Shoigu dismissed claims that Moscow might use nukes in the neighboring country as "absurd," saying there are no targets in Ukraine that would warrant doing so.

Russia's current nuclear doctrine allows for the use of nuclear weapons in the event of a first nuclear strike on its territory or infrastructure, or if the existence of the Russian state is threatened by either nuclear or conventional weapons.