Ukrainian forces have managed to stave off a furious Russian offensive in the key eastern city of Syevyerodonetsk, President Volodymyr Zelenskiy said as Moscow’s unprovoked invasion of Ukraine entered its 100th day on June 3.

Meanwhile, NATO has said that the conflict has become “a war of attrition,” which has seen Russia fail to achieve its initial goal of a blitz victory.

“We have some success in the battles in Syevyerodonetsk,” Zelenskiy said in his late-night address on June 2, adding, “But it’s too early to tell.” He said that overall the situation remains “very difficult.”

Britain’s Ministry of Defense said in its daily intelligence bulletin on June 3 that, compared to Russia’s original plan, none of Moscow’s strategic objectives have been reached.

“Russian forces failed to achieve their initial objectives to seize Kyiv and Ukrainian centers of government,” the British bulletin said. “Staunch Ukrainian resistance and the failure to secure Hostomel airfield [near Kyiv] in the first 24 hours led to Russian offensive operations being repulsed.”

House-to-house fighting has been continuing in Syevyerodonetsk, 80 percent of which is controlled by Russian forces, according to officials, as Ukrainian forces struggle to hold off Russian troops while they await the arrival of advanced weapons that Washington has pledged to deliver.

Serhiy Hayday, the head of Luhansk region military administration, said that some 800 people, including children, remain hiding in bomb shelters underneath a chemical factory in the city. Those hiding are local residents who were asked to leave the city, but refused, according to Hayday.

Ukrainian forces said on June 3 that they made significant progress during an offensive against Russian positions in the occupied southern region of Kherson. The Territorial Defense AZOV Dnipro unit said its forces liberated 8 kilometers of “occupied territory.”

Western officials estimate that the deliveries of advanced weapons systems to Ukraine are about three weeks away, and Ukrainian forces are bracing for further Russian aggression.

Earlier on June 2, Zelenskiy told the Luxembourg parliament in a video address that Russia was in control of one-fifth of Ukraine’s territory. That is equivalent to 125,000 square kilometers or, as Zelenksiy put it, “more than the entire Benelux” — a shorthand term for Belgium, the Netherlands, and Luxembourg.

British intelligence estimated in its bulletin that Russia now controls more than 90 percent of the Luhansk Oblast in eastern Ukraine and is likely to have complete control of the region in the next two weeks.

But the bulletin cautioned that Russia’s recent tactical successes have come at a significant cost in terms of resources and this trend will likely continue.

“In order for Russia to achieve any form of success [it] will require continued huge investment of manpower and equipment, and is likely to take considerable further time,” the British intelligence bulletin concluded.

In Washington, NATO chief Jens Stoltenberg said the conflict has become “a war of attrition.”

“Wars are by nature unpredictable and therefore we just have to be prepared for the long haul,” Stoltenberg told reporters after meeting U.S. President Joe Biden at the White House.

The war most likely will end at the negotiating table, he said, adding that what happens during talks is closely linked to the situation on the battlefield.

In Kyiv, the new U.S. ambassador to Ukraine said after presenting her credentials to Zelenskiy that the delivery of U.S. military aid is being accelerated.

“My understanding is that now it’s very quick, within days, less even, of a decision, that the hardware is in Ukrainian hands,” Ambassador Bridget Brink said.

But senior Pentagon officials have said that the most advanced U.S. rocket systems — the HIMARS, which can strike targets as far as 80 kilometers away, will take at least three weeks to reach the battlefront, raising questions as to whether they will arrive in time to stop Russia’s slow but steady gains.

Kremlin spokesman Dmitry Peskov again warned on June 2 of “absolutely undesirable and rather unpleasant scenarios” if the latest Western-supplied weapons were used against Russia.