MOSCOW (AFP) - Russian President Vladimir Putin was set to hold his end-of-year press conference Thursday (Dec 23) with fears mounting in the West that his sabre-rattling is a precursor for a major military escalation in Ukraine.

Senior Kremlin and defence officials have grown increasingly insistent that the West and Nato are trampling Moscow's security red lines and encroaching dangerously close to Russia's borders.

Moscow presented the West with sweeping security demands last week, saying Nato must not admit new members and barring the United States from establishing new bases in former Soviet countries.

The growing tensions peaked this week when Mr Putin vowed that Russia would take "appropriate retaliatory" military steps in response to what he called the West's "aggressive stance".

In an address to defence officials, he announced that a new arsenal of hypersonic missiles that he has previously described as "invincible" were nearing combat readiness.

But the Russian leader, whose officials have demanded negotiations with Nato and the United States, suggested that any accords with Washington would be worthless since it "easily withdraws from all international treaties".

Mr Putin, in power for more than two decades, was a loyal servant of the USSR and a KGB agent during the Soviet Union.

He has described its collapse three decades ago as "the greatest geopolitical disaster of the 20th century".

Moscow in 2014 annexed the Crimean peninsula from Ukraine in the wake of a popular uprising that ousted a pro-Putin president and sparked a conflict with separatists who won Russia's political backing.

Washington and Brussels, which have sounded the alarm over a massive Russian troop build-up around Ukraine, have long accused Moscow of providing direct military support to the breakaway fighters in a conflict that has killed over 13,000 people since 2014.

The West has warned of crippling economic repercussions if Mr Putin launches an assault and US officials have already said that some of the Russian proposals are "unacceptable" ahead of planned talks early next year.

The press conference is also expected to see questions on an unprecedented wave of arrests at home against voices the Kremlin has deemed critical of its tightening grip on power.

It will coincide with a high-profile court case in Moscow where the esteemed rights group Memorial was on trial for violations of "foreign agent" legislation.

This year has seen a historic clampdown on the opposition, with its most prominent leaders exiled or jailed, but the announcement of the case against the respected rights group was seen as a dramatic downturn.

In what appeared to be an ominous sign, Mr Putin earlier this month said that Memorial had been advocating on behalf of "terrorist and extremist organisations".

The case follows other key trials, including the jailing of Russia's most prominent opposition figure Alexei Navalny and the closure of his anti-corruption and political organisations on extremism convictions.

That crackdown, as well as allegations of election meddling and Russia's support for the Syrian regime, have resulted in a wave of US and European sanctions against Moscow.

Mr Putin usually uses his end-of-year briefing to rattle off facts and figures illustrating Russia's economic prowess, but those penalties have exacerbated the country's mounting economic woes.

Inflation has surged this year to nearly double the Central Bank's target of four percent, pushing up prices of everyday items.

The pandemic has also compounded problems for cash-strapped Russians and the coronavirus has claimed more lives in Russia than any other European country, despite the widespread availability of free homemade vaccines.

The Rosstat statistics agency says some 520,000 Russians with Covid have died over the pandemic.