U.S. Secretary of Defense Lloyd Austin, right, and Ukraine’s President Volodymyr Zelenskyy shake hands during their meeting in Kyiv, Ukraine. Press Service Of The President Of Ukraine via the associated press.

By ERIC SCHMITT | THE NEW YORK TIMES

KYIV, Ukraine — Defense Secretary Lloyd Austin made an unannounced visit to Kyiv on Monday to bolster support for the war effort as Ukrainian forces steadily lose ground to Russian troops and allies stop short of fully endorsing Ukraine’s latest plan to end the conflict.

The visit by Austin, his third to Ukraine since Russia’s full-scale invasion began in February 2022, comes three days after President Joe Biden met with allied leaders in Germany to rally support for Ukraine, and with the fate of future American military aid to the country hanging in the balance of the U.S. presidential election in two weeks.

Austin, who arrived by train from Poland, met with President Volodymyr Zelenskyy and top Ukrainian military leaders to discuss how to continue backing Ukraine’s military campaign against a growing set of challenges.

In his meeting with Zelenskyy, Austin announced that the Pentagon would send Ukraine a new $400 million shipment of arms, including ammunition for HIMARS rocket systems, additional munitions, armored vehicles and anti-tank weapons.

In recent days, Russian troops have clawed back much of the territory Ukraine seized in Russia’s western Kursk region. The Russians are also making slow, grinding progress in the Donbas region of eastern Ukraine, despite staggering casualties. And Moscow has sharply increased its drone attacks across Ukraine.

“We’re going to continue to support Ukraine and its efforts to defend its sovereign territory,” Austin told reporters traveling with him to Kyiv, Ukraine’s capital.

The United States has provided Ukraine more than $61 billion in security aid since the start of the war.

Austin also said U.S. officials would help Ukraine train and equip new units it is building. Reports have surfaced that many Ukrainian units fighting in southern Donetsk and other front-line areas are short of troops.

“They’re working hard to bring more people on board,” Austin told reporters. “They’ve got to train those people. They have to regenerate combat power.”

Away from the battlefield, Ukraine is also facing headwinds.

Zelenskyy told EU leaders last week in Brussels that his country desperately needed their support for his plan to end the war, which he maintains could happen no later than next year.

A major point in Zelenskyy’s so-called victory plan is for Ukraine’s accession into the NATO military alliance — a proposal that American officials have balked at, fearing it could drag the United States directly into the war.

Zelenskyy’s strategy also calls for the West to lift restrictions on Kyiv’s use of missiles provided by the West to strike ammunition depots and other military facilities deep inside Russia, and to share more satellite data that Ukraine can use to identify and strike Russian targets.

The Biden administration has repeatedly rejected such moves. Biden has been wary about provoking retaliation against U.S. interests. American intelligence agencies have concluded Russia is likely to retaliate with greater force if the United States and its allies permit Ukraine to fire long-range missiles into Russia. And Austin has said Ukraine already produces its own formidable attack drones in large numbers that can strike targets much deeper inside Russia than the Western missiles.

Much of Austin’s day in Ukraine’s capital was expected to be filled with meetings to discuss battlefield updates and strategy for the coming months, including Ukraine’s desperate need for more air defenses to ward off Russian missile and glide-bomb attacks aimed at destroying the country’s electrical grid as winter approaches.

In addition, Russia has significantly increased drone strikes against Ukrainian targets across the country. Attacks have increased from 350 strikes in July, to 750 in August, to 1,500 in September, according to two Western officials.

Ukraine’s offensive into Kursk in August caught U.S. officials — as well as Russian commanders — by surprise. Besides bolstering troop and public morale, the incursion had two primary objectives: to force the Kremlin to divert soldiers from other parts of the front to respond to the attack, thereby easing pressure on Ukrainian forces, and to capture territory that Russia will seek to reclaim, potentially forcing it to come to the negotiating table.