Ukraine’s Zelensky Urges Faster Weapons Deliveries Amid Russian Push

“The speed of supply has been and will be one of the key factors in this war,” he said. “Russia hopes to drag out the war, to exhaust our forces. So we have to make time our weapon. We must speed up the events, speed up the supply and opening of new necessary weaponry options for Ukraine.”

The U.S., Germany and other European countries committed last week to supply Kyiv with battle tanks, but it will be several months before they can be deployed in combat. 

During a visit to South Korea on Monday, North Atlantic Treaty Organization Secretary-General

Jens Stoltenberg

urged Seoul to provide military support to Ukraine, saying the country was in urgent need of ammunition. South Korea has sent materials such as gas masks, bulletproof vests and medical supplies to Ukraine, but has declined to provide lethal weapons, citing a law that prevents it from providing arms to countries engaged in conflicts.

After months of failed assaults on Bakhmut, a city in Ukraine’s east, Russian forces are moving to surround it at the intersection of several major roads. Fending off Russian attacks there is proving increasingly difficult, according to Ukrainian forces in the area. 

Control over Bakhmut would help Russia advance on other cities in Ukraine’s eastern Donbas area, which President

Vladimir Putin

has identified as the primary objective of his campaign in Ukraine. It would also be a major symbolic prize after months of grinding combat that have turned Bakhmut into an epicenter of the war, with thousands of soldiers killed and wounded on both sides.

Denis Pushilin,

the head of a part of eastern Ukraine that Moscow cleaved from the country in 2014, said Russian forces were advancing in the main areas of Bakhmut, but that it was too soon to say that Russian forces had managed to encircle the city. 

Cutting off the road that is used to supply Ukrainian forces in Bakhmut from Chasiv Yar, which is due west, is now a priority, Mr. Pushilin said.

Russian forces have also entrenched themselves in the eastern part of Vuhledar, another Donetsk town, he said.

Meanwhile, Ukrainian forces appeared to be attacking supply lines to the Russian-occupied Crimean Peninsula over the weekend. A railway bridge near the city of Melitopol in the occupied part of the southern Zaporizhzhia region was hit by Ukrainian forces, the Russian-backed governor, Yevgeniy Balitsky, said Sunday.

Four civilians were killed and five were injured in the strike by a U.S.-made multiple-rocket launcher known as a Himars, Mr. Balitsky said in a statement posted on social media.

The recent push comes as Russia seeks to build momentum after seizing the town of Soledar, just outside Bakhmut, earlier in January in its first significant success for months. In the south, Russian forces are also pressing an offensive in the Zaporizhzhia region, also claimed by Moscow.

An influx of Russian troops—many of them convicts who have joined Russian paramilitary group Wagner as well as soldiers recently mobilized by the regular army—has given Moscow a manpower advantage.

The U.K.’s Ministry of Defense said Russian authorities were likely leaving the door open to further rounds of mobilization. Russian presidential spokesman Dmitry Peskov last week said a decree on “partial mobilization” remained in force to support the work of the armed forces. He declined to say, however, whether more people would be drafted soon.

 “The Russian leadership highly likely continues to search for ways to meet the high number of personnel required to resource any future major offensive in Ukraine, while minimizing domestic dissent.”

—Bojan Pancevski contributed to this article.

Write to Isabel Coles at isabel.coles@wsj.com