Last month, President Joe Biden's decision to help Ukraine get F-16 fighter jets marked yet another crossing of a Russian "

Despite the Russian leader's apocalyptic warnings, the US gradually agreed to expand Ukraine's arsenal with Javelin and Stinger missiles, HIMARS launchers, advanced missile defense systems, drones, helicopters, M1 Abrams tanks, and soon fourth-generation fighter jets..

“A key reason for ignoring Putin’s threats, according to US officials, is a dynamic that has been observed since the early days of the war: the Russian president did not keep his promises to punish the West for providing weapons to Ukraine.. His bluff has given American and European leaders a measure of confidence that they can continue to do so without serious repercussions,” writes the Washington Post, adding that one of the biggest uncertainties of the war remains the extent to which such an approach will work..

[see_also ids\u003d"

“Russia has devalued “its red lines” so many times by saying certain things will be unacceptable and then doing nothing when they happen.. The problem is we don't know where the red line is. It's in one person's head, and it can change every day,” said Maxim Samorukov, Russia expert at the Carnegie Endowment for International Peace..

U.S. officials say managing escalation risk remains one of the hardest aspects of the war for Biden and his foreign policy advisers.. In deciding to provide Ukraine with new weapons systems, they are focusing on four key factors.

Do they need such a weapon? Can they use it? Do we have it? What will be the reaction of Russia? ' said one State Department official.

The official said Russia's reluctance to retaliate has affected how Secretary of State Anthony Blinken assesses risks. Namely, he became a key Biden confidant and a powerful voice encouraging the administration and US allies to do more to support Ukraine..

“Things like this need to be taken into account when making decisions.. We did something but there was no escalation or response. Is there anything else we can do? We constantly weigh these factors. And that was the hardest decision we have to make,” the official said..

[see_also ids\u003d"

Like Blinken, White House national security adviser Jake Sullivan also believes the benefits of giving Ukraine more lethal weapons outweigh the risks of escalation.. He is actively working with European allies on the issue of providing Ukraine with F-16 fighters, a White House official said..

The administration has been juggling these issues amid uproar from Ukrainians and congressional hawks who are frustrated with the piecemeal approach and want Biden to move faster and send more modern equipment to the battlefield amid brutal Russian pressure..

Although Putin defied the US by suspending participation in a critical nuclear arms control treaty, arresting Wall Street Journal reporter Evan Gershkovich and sentencing WNBA star Britney Griner to a nine-year prison sentence before insisting on trading her for a notorious arms dealer.

But Western officials are aware that this does not mean that he will never do it - especially as the conflict escalates.. On Tuesday, drone strikes targeted an elite area of \u200b\u200bMoscow in what one Russian politician called the worst attack on the capital since World War II.. Ukraine denies any involvement in such strikes on Russian territory. And the Biden administration has said it does not encourage such Ukrainian attacks.. However, Kiev seems pleased that Russian civilians are experiencing the fear that Ukrainians have been living with for more than a year, as their communities are subject to continuous Russian and drone attacks..

A possible explanation for Putin's reluctance to hit the West could be the deterioration of the Russian military, US officials say..

“It does not seem to be in their interest now to engage in a direct confrontation with NATO.. They don't have the capacity to do so,"

[see_also ids\u003d"

The head of the Joint Chiefs of Staff, General Mark Milley, in a recent interview with Foreign Affairs estimated that Russia has lost up to 250,000 soldiers killed and wounded since the start of the full-scale invasion.. These are staggering losses for any conflict.. As the number of dead and wounded Russian soldiers rises, Putin has refocused his military objectives, from seizing control of Kiev and decapitating the Ukrainian government to controlling and annexing parts of eastern and southern Ukraine..

Yet US officials remain wary that Russia, with the world's largest nuclear arsenal, could escalate in Ukraine or elsewhere.. Last year, amid growing concerns that Russia was considering deploying nuclear weapons, State Department officials privately warned Moscow of the consequences of such a move.. This was followed by public warnings..

In the Biden administration, the Pentagon is seen as more cautious than the White House or State Department about providing Ukraine with more sophisticated weaponry, but officials deny fear of escalation plays any role in their calculus..

According to a senior Pentagon official, the US defense establishment is focused on what Ukraine needs at any given moment.. The official gave an example of how the US went from providing anti-tank missiles like the Javelin when it was clear convoys of Russian military equipment would invade Ukraine to sending artillery when the war turned into a bloody duel. And now the West has decided to provide the Ukrainian army with tanks and F-16 fighters.

[see_also ids\u003d"

Undoubtedly, the Biden administration's willingness to cross Putin's red lines has strengthened Ukraine's ability to defend itself and reclaim territory in the east and south.. However, it remains to be seen whether Putin will continue to allow the West to ignore his threats with impunity..

“Certain red lines exist, but since we can’t know for sure what they are, this poses a risk,” said Alexander Gabuev, director of the Carnegie Eurasia Center in Berlin..