BERLIN (NYTIMES) - Russia took new steps on Friday (May 20) to gird for an escalating struggle with the West over the war in Ukraine, moving to expand military recruitment to older citizens and severing gas supplies to Finland in apparent retaliation for its Nordic neighbour's application to join the Nato alliance.

The two developments reflected the mounting pressure on Russia because of its three-month-old invasion of Ukraine, which has evolved into something of a stalemate that has seriously depleted the Kremlin's conventional war capabilities, even as Russia has made some incremental gains.

The conflict has also left Russia increasingly vulnerable economically and energised Western opposition in ways that President Vladimir Putin had sought to prevent.

Both Sweden and Finland broke with their longstanding policies of neutrality and applied to join Nato over the past week, a vote of confidence in the unity of an alliance that has been cemented by the conflict.

Russia said on Friday that it was suspending gas shipments to Finland because the Finnish gas company had failed to make payments in roubles. But the Kremlin has used Russia's energy supply as a political weapon in the past and previously threatened "retaliation" against Sweden and Finland should they move to join Nato.

Last weekend, Moscow suspended electricity exports to Finland after the country's intention to join the alliance became clear.

The Finnish company, Gasum, called the latest move from the Russian gas giant Gazprom "highly regrettable" but said that it did not expect disruptions.

“It is very unfortunate that the supply of natural gas under our supply contract will now run out,” Gasum chief executive Mika Wiljanen said in a statement.

“However, we have prepared carefully for this situation and if there are no disruptions in the gas transmission network, we will be able to supply gas to all our customers in the coming months.”

Gas exports are vital to Russia’s economy. They also give Moscow a potent diplomatic tool: Last month, Russia halted natural gas supplies to Poland and Bulgaria, two Nato countries that are dependent on Russian gas but have strongly opposed the war in Ukraine. Poland and Bulgaria also had balked at making payments in roubles.

Russia's reaction underscored the geopolitical fallout from the war in Ukraine as it spurs what could become one of the most radical redrawings of Europe's security order in decades.

That fallout spread further on Friday as the state-controlled Russian oil giant Rosneft announced that Mr Gerhard Schröder, former chancellor of Germany and one of Putin's last prominent Western cheerleaders, would be stepping down as chair of the board.

Moscow is increasingly mired in difficulties on the ground in Ukraine, a former Soviet republic that Mr Putin does not consider a legitimate country.

His plan for a quick subjugation of Ukraine after the Feb 24 invasion has been upended by a series of bruising battles that have forced him to reduce his territorial ambitions and have left Russia’s forces exhausted and its equipment diminished.

Under pressure to score victories and shore up its forces for an intensifying battle in the Donbas region of eastern Ukraine, Moscow on Friday moved to expand the pool of potential recruits to its military by eliminating the age limit for service.

An amendment introduced by senior lawmakers in Russia's Parliament would allow Russians older than 40 to sign first-time military service contracts. Under the current law, Russian citizens must be aged 18 to 40 to sign a first-time contract.

The law would bring in more service members with specialties, such as medical workers and engineers, a statement from the lower house of Parliament said.

“Highly professional specialists are needed” to operate military equipment, the statement said.

It made no mention of a manpower shortage in the field. But experts say that Russia suffers that shortage and is under strain, particularly after a series of humiliating setbacks in trying to capture Ukraine’s capital, Kyiv, and more recently in failing to seize the country’s second-largest city, Kharkiv.

Mr Putin has resisted ordering a large-scale military draft, apparently fearing domestic backlash, and is instead stepping up recruitment.

The lack of reserve troops is forcing Russian commanders to consolidate depleted battalion tactical groups, according to the Institute for the Study of War, a Washington-based research group that has been monitoring the conflict.

The institute quoted an unidentified US defence official as saying that Russian forces have had to disband and combine some battalion tactical groups in Ukraine to compensate for casualties and other losses.

At the same time, the institute said that some Russian troops who had been withdrawn from around Kharkiv, in the north-east of the country, have been redeployed towards the Donetsk region in Donbas.

Even as Russia’s war aims have narrowed, it was fortifying control over parts of Ukraine this week.

After the near-total conquest of the south-east port city of Mariupol, Russian officials appeared to be laying the groundwork for annexing swathes of south-east Ukraine.

They have already made changes in some areas, introducing the rouble currency, installing proxy politicians and cutting the population off from Ukrainian broadcasts.

Units that fought in Mariupol can now be sent elsewhere following the surrender of Ukrainian fighters defending a large steel plant. A Russia Defence Ministry spokesman, Major General Igor Konashenkov, said on Friday that its forces had full control of the plant, which has been “completely liberated”.

The focus has shifted to the eastern battlefield. In the Donbas region, which Russia has vowed to capture after having abandoned more ambitious goals of toppling the central government, Russian troops carried out 13 attacks on Ukrainian positions, the Ukrainian military said.

A weeks-long fight around the city of Severodonetsk, in the Luhansk region, has intensified in the past day, with Russian forces on Friday firing artillery at a school where more than 200 people were sheltering, killing three of them, a regional military official said.

Russian artillery fire into the city and nearby areas killed 12 civilians and damaged more than 60 buildings over the past day, said the governor of Luhansk province. The Ukrainian military said Friday in its regularly published morning assessment of the war that its forces had repelled a Russian attempt to storm defensive positions near Severodonetsk.

To help keep the Ukrainian war effort running, the Group of 7 major economic powers on Friday agreed to provide nearly US$20 billion (S$28 billion) in grants and loans to support Ukraine's economy over the coming months.