Delays in weapons deliveries from Western allies to Ukraine are opening a door for Russian battlefield advances, Ukrainian President Volodymyr Zelensky said, making the fight “very difficult” along parts of the front line where the Kremlin’s forces captured a strategic city last weekend ahead of the war’s two-year anniversary.

Mr Zelensky and other officials have often expressed frustration at the slowness of promised aid deliveries, especially since signs of war fatigue have emerged.

European countries are struggling to find enough stocks to send to Kyiv, and US help worth 60 billion US dollars is stalled over political differences.

That appears to be playing into the hands of Russian President Vladimir Putin.

Even so, more help is heading Ukraine’s way, as Sweden announced Tuesday its biggest aid package so far and Canada said it was expediting the delivery of more than 800 drones.

Mr Zelensky, in his daily video address late on Monday, said Russia has built up troops at some points along the 930-mile front line, apparently aiming to pounce on any perceived defensive weaknesses.

“They (the Russians) are taking advantage of delays in aid to Ukraine,” he said after visiting the command post in the area of Kupiansk, in the northeastern Kharkiv region.

He said Ukrainian troops keenly felt a shortage of artillery, air defensc systems and long-range weapons.

Ukrainian forces withdrew from the strategic eastern city of Avdiivka at the weekend, where they had battled a fierce Russian assault for four months despite being heavily outnumbered and outgunned.

But Oleksiy Danilov, head of Ukraine’s National Security and Defence Council, said that while the situation on the battlefield is hard, especially due to a lack of ammunition, the situation on the eastern front is not catastrophic.

“We fight and will continue to fight,” he told news outlet Ukrainska Pravda.

“We have only one request to our partners: to help with weapons, with ammunition, and with air defence.”

He claimed that Russia racked up heavy losses of troops and equipment in the fight for bombed-out Avdiivka.

His claim could not be independently verified.

Mr Zelensky said talks with foreign partners are focusing on how to “resume and extend” support.

Sweden, which is poised to join Nato, said it will donate military aid to Ukraine worth 7.1 billion kronor (681 million US dollars).

That includes 30 boats, some of which are fast and powerful military assault craft, and underwater weapons.

The deal also includes artillery ammunition, Leopard tanks, shoulder-borne anti-aircraft defence systems, anti-tank missiles, grenade launchers, hand grenades and medical transport vehicles, as well as underwater drones and diving equipment.

“By supporting Ukraine, we are also investing in our own security,” defence minister Pal Jonson told a news conference in Stockholm.

“If Russia were to win this terrible war, we would have significantly greater security problems than we have today.”

The Canadian government said it will dispatch more than 800 drones to Ukraine starting as early as this spring.

Ukraine last year received 42.5 billion US dollars from foreign partners, of which 11.6 billion US dollars was in non-repayable grant aid, Ukraine’s Ministry of Finance said Tuesday.

The grant assistance was provided by the US, Japan, Norway, Germany, Spain, Finland, Switzerland, Ireland, Belgium, and Iceland, it said.

The US provided the biggest amount of non-repayable grant aid, with 11 billion US dollars.

Long-term concessional financing amounted to 30.9 billion US dollars, which included loans from the European Union (19.5 billion US dollars), the International Monetary Fund (4.5 billion US dollars), Japan (3.4 billion US dollars), Canada (1.8 billion US dollars), the UK (one billion US dollars), the World Bank (660 million US dollars) and Spain (50 million US dollars).

Meanwhile, Ukraine shot down all 23 Shahed drones that Russia launched on Monday night over various regions of the country, the country’s air force said.

Air force spokesman Yurii Ihnat said Russian aircraft activity had dropped off after Ukraine recently shot down a number of enemy warplanes.

The air force commander, Mykola Oleschuk, said that his troops destroyed Su-34 and Su-35 bomber jets.

Over the weekend he said that other Russian jets were shot down.