Russia Doing ‘Everything’ to Stop Ukraine’s Counteroffensive, Zelensky Says

President Volodymyr Zelensky of Ukraine said that Russian forces were throwing “everything they can” at Kyiv’s troops fighting to retake land in the south and east, again emphasizing the grueling nature of a counteroffensive that is moving more slowly than some allies had hoped.

Ukrainian troops have made only small gains since launching the widely anticipated campaign in June, and in recent weeks, they appear to have stalled in some areas in the face of staunch Russian defenses. Casualties are mounting, and American officials have said that Ukraine has also lost newly provided Western armored vehicles in field after field of land mines.

Mr. Zelensky, who has defended the pace of the counteroffensive, said in his overnight address late Friday that he had had a “detailed” meeting earlier in the day with his top commanders to discuss the front lines and “logistics” — including weapons and the “rational use of shells, supplies from partners,” an apparent reference to the rate at which Ukraine’s forces are expending ammunition.

“We must all understand very clearly — as clearly as possible — that the Russian forces on our southern and eastern lands are investing everything they can to stop our warriors,” he said. “Every thousand meters of advance, every success of each of our combat brigades deserves gratitude.”

Mr. Zelensky has repeatedly pressed his Western allies for increasingly sophisticated weapons, and he secured new pledges this week from allies at the NATO summit in Lithuania, including long-range missiles from France and more tank ammunition from Germany. But it was not immediately clear how soon those weapons would arrive, or how significant a boost they could provide for the counteroffensive.

One ally that has resisted sending weapons to Ukraine is South Korea, whose president, Yoon Suk Yeol, arrived in Ukraine on Saturday for an unannounced visit. In a statement after his meeting with the South Korean leader, Mr. Zelensky made no mention of whether they had discussed lethal military assistance.

The United States has acknowledged that Ukrainian forces are running low on ammunition, which was one reason that President Biden agreed last week over the objections of allies to send cluster munitions to Ukraine. The weapons are highly dangerous for civilians and are outlawed by all but a few countries, including the United States, Russia and Ukraine.

Ukraine’s top commander, Gen. Valeriy Zaluzhnyi, told The Washington Post in an interview published on Friday that his military was still lacking the necessary resources to defeat Russia and criticized allies who have argued that it does not need F-16s.

The defense ministers of Denmark and the Netherlands announced this past week that they had gathered 11 countries to help train Ukrainian pilots on F-16 fighter jets as soon as next month. Mr. Biden agreed in May to drop his objections to giving Ukraine F-16s, though that may not happen until next year.

Ukraine has also been asking the United States for long-range Army Tactical Missile Systems, which have a range of about 190 miles — about 40 miles more than missiles that France and Britain are providing. American and European officials have said that the Biden administration, after months of maintaining it would not provide the weapons for fear of further provoking Russia, is considering whether to send a few to Ukraine.

While Mr. Yoon’s visit to Ukraine did not appear to have changed Seoul’s stance on weapons, the trip was a notable show of support.

Seoul, which is reluctant to openly antagonize Moscow, has declined to send lethal aid and has imposed strict export control rules on its global weapons sales. It has also provided humanitarian aid and financial support to Ukraine for mine removal, power grid restoration and reconstruction projects.

However, Mr. Yoon has indicated that Seoul might be willing to consider sending Ukraine military aid in the event of a large-scale attack on civilians.

He visited the towns of Bucha and Irpin — which became synonymous with Russian atrocities in the earliest days of the invasion — upon arrival on Saturday, Mr. Yoon’s office said, and then met with Mr. Zelensky.

After the meeting, Mr. Zelensky said he was “grateful” to Mr. Yoon for supporting Ukraine’s efforts for peace and security — along with “new initiatives of financial, technical and humanitarian support.”

In the meantime, Ukraine’s military continued to report fierce fighting in the country’s south and east, saying that Russian forces in southern Ukraine were focused on “preventing the further advance” of Kyiv’s troops fighting in the direction of two key Russian-occupied cities, Melitopol and Berdiansk.

Here’s what else is happening in the war:

• Russian shelling killed one man and injured another in the Kharkiv region of northeastern Ukraine, the regional military administration said in a statement.

• A spokesman for Ukraine’s border service said that “available information shows” that some fighters with the Wagner mercenary group had “been observed in Belarus.” The comments came a day after Belarus’s Ministry of Defense said Wagner mercenaries were training its security forces. Questions about the fighters’ future have swirled since a deal to end their mutiny in Russia last month included an arrangement for voluntary exile in Belarus. There is little evidence they have gone there in large numbers.

• President Vladimir V. Putin of Russia told President Cyril Ramaphosa of South Africa in a phone call, two days before a U.N.-brokered agreement that enables Ukraine to export its grain is set to expire, that commitments to Moscow set out by the deal remained “unfulfilled,” the Kremlin said.

  Russia has repeatedly threatened to pull out of the deal, complaining that Western sanctions have restricted the sale of its agricultural products. The conversation comes as South Africa grapples with Mr. Putin’s possible attendance at a summit in Johannesburg. Mr. Putin faces an arrest warrant from the International Criminal Court, and as a member of the court, South Africa is obligated to arrest him if he enters.

John Yoon contributed reporting from Seoul.