US Secretary of State Antony Blinken said Ukraine has to “make its own choice” when deciding to use US-made weapons to strike targets inside Russia .

"We've not enabled or encouraged strikes outside of Ukraine, but ultimately, Ukraine has to make decisions for itself about how it's going to conduct this war," he said during a visit to Kyiv on May 15.

The remarks are a significant softening of the previous demands that Ukraine must not use Nato-made weapons on targets inside Russia, because of fears of escalation and provoking a retaliatory strike by Russia against a Nato country.

The Russian Ministry of Foreign Affairs (MFA) responded with a strongly worded statement that reminded the West that Russia’s military doctrine allows it to use nuclear weapons if attacked.

“The Kyiv regime and its Western masterminds should at long last admit that their reckless steps are pushing the situation ever closer towards the explosive tipping point,” the Russian MFA said in a social media post. “The military risks this is creating and the ensuing threats to our country have clearly been outlined in the Military Doctrine of the Russian Federation and the Basic Principles of State Policy of the Russian Federation on Nuclear Deterrence.”

Russia's military doctrine says that if the country faces an “existential threat” then it is allowed to use nuclear weapons. Russian President Vladimir Putin has repeatedly used the threat of a nuclear exchange to contain Western support for Ukraine. Nato has said from the outset of the war in Ukraine that avoiding a WWIII is its top priority.

However, as Ukraine’s military situation deteriorates due to the tardy provision of support by the US over the last six months, Ukraine’s western allies are softening the restrictions they have placed on the use of their materiel in an effort to shore up the Armed Forces of Ukraine (AFU)’s position.

Recently the US complained about Ukraine using its own drones to strike Russian oil refineries deep inside Russian territory. Ukraine should avoid hitting the refineries and choose “military targets” instead.

But the US has softened its stance on that objection too, as bne IntelliNews reported, it has transpired that the strategy of hitting oil refineries is working.

Blinken’s comments follow on the heels of similar comments made by British Foreign Minister Lord David Cameron, who said during a similar trip to Kyiv that the UK would not object if Ukraine used British-made missiles to strike targets inside Russia.

The Kremlin issued a stern objection, warning that Russia would respond by targeting UK assets “in Ukraine and outside.”

Blinken was asked at a press conference on May 15 about Ukrainian complaints that the ban on using Nato-made weapons to hit targets in Russia had contributed to Ukraine’s losses as Russia openly built up its forces inside Russian territory before crossing the border into Kharkiv Oblast as part of its latest devastating assault.

"We saw their military sitting one or two kilometres from the border inside Russia, and there was nothing we could do about that," Oleksandra Ustinova, the head of the Ukraine's parliamentary commission on arms and ammunition, told Politico.

In particular, the US has provided Ukraine with long-range ATACMS missiles, which Ukraine has already used to strike targets in occupied Crimea, which is not considered by the allies to be Russian territory.

"The main problem right now is the White House policy to limit our capability" to strike military targets inside Russia, said David Arakhamia, the parliamentary leader of President Volodymyr Zelenskiy's party, the Servant of the People, the Kyiv Independent reports.

With tensions ratcheting up even higher in the face of the creeping escalation, Russian President Vladimir Putin ordered snap nuclear missile exercises last week of non-strategic nuclear weapons.

“We would like to point out that these drills should be viewed in the context of the recent militant statements made by Western officials and the highly destabilising actions taken by several Nato countries to increase military pressure on the Russian Federation,” the Russian MFA said in a statement.

“The matter concerns above all the open declaration of support for and the provision of direct assistance to the terrorist attacks against Russia carried out by the Kiev regime with the use of increasingly more advanced Western weapons provided to it,” the MFA said.

The MFA highlighted the use of US-made ATACMS missiles being provided to Ukraine, which have been recently sent to Ukraine and are capable of reaching targets inside Russia.

“At the same time, attempting to build up multifaceted missile threats to Russia, the US has openly and manifestly launched the deployment of ground-based intermediate- and shorter-range missiles, which were previously prohibited under the INF Treaty, around the world,” the MFA said, referring to a Cold War missile control agreement that is no longer in force.

“We hereby expressly declare that we reserve the right to respond in kind, no matter where US-made intermediate- and shorter-range missiles are deployed, which would amount to the termination of Russia’s unilateral moratorium on the deployment of these weapon systems,” the MFA said.