KYIV, Ukraine >> Ukrainian forces withdrew from some parts of the country’s northeast and battled Russian troops in other areas Wednesday, as President Volodymyr Zelenskyy’s decision to postpone all his upcoming foreign trips underscored the seriousness of the threat his soldiers face.

Against that grim backdrop, visiting U.S. Secretary of State Antony Blinken sought to reassure Ukraine of continuing American support, announcing a $2 billion arms deal. Most of the money comes from a package approved last month.

The top diplomat’s trip comes as Russian troops press a new offensive in Ukraine’s Kharkiv region. It began last week, marking the most significant border incursion since the full-scale invasion began in 2022 and forcing thousands to flee their homes. In recent weeks, Moscow’s forces have also sought to build on gains in the eastern region of Donetsk. Taken together, the developments mean the war has entered a critical stage for Ukraine’s depleted army.

Ukraine’s General Staff reported late Tuesday that troops fell back from two areas in Kharkiv — Lukyantsi and Vovchansk — “in order to save the lives of our servicemen and avoid losses.” Russia said it had captured Lukyantsi.

It was not possible to independently verify either side’s claims.

Vovchansk — just 5 kilometers (3 miles) from the Russian border — has been the focus of much of the recent fighting, and Ukrainian and Russian troops battled in its streets Wednesday. Oleksii Kharkivskyi, head of the city’s patrol police, said Russian troops were taking up positions in the city, while the Ukrainian General Staff said its forces were trying to flush them out.

Gunfire could be heard in the background of a video the police official posted on his Instagram page.

The Ukrainian presidential office said additional reinforcements were being deployed in the region, including army reserve units.

At the dangerous juncture, Blinken was in Ukraine to highlight U.S. support, though most of the money he announced Wednesday, about $1.6 billion, comes from the $60 billion allotted to Ukraine in the supplemental foreign assistance legislation passed by Congress and signed by President Joe Biden, officials said.

He said the money would be used for three purposes: to provide weapons in the short term, to invest in Ukraine’s defense-industrial base and to allow Ukraine to buy military supplies from other countries.

At a news conference with Blinken, Ukrainian Foreign Minister Dmytro Kuleba said of the aid: “This is a very powerful message to both our friends and our enemies.”

Blinken said Washington understands the urgency of Ukraine’s need for additional air defenses to protect against the Russian onslaught and was prioritizing them in its assistance.

He added that the U.S. has “not encouraged or enabled strikes outside of Ukraine” using American-supplied long-range weapons. That decision is up to Kyiv authorities, he said.

The United Kingdom has said it placed no limits on Ukraine’s use of weapons Britain supplies to hit targets on Russian soil, but Germany, another major supporter, has balked at that and ruled it out for fear of escalating the conflict.

Russia is opening new fronts in order to stretch Ukraine’s army, which is short of ammunition and manpower, along the about 620-mile front line, hoping defenses will crumble. Russian artillery and sabotage raids have also been menacing Ukraine’s northern Chernihiv and Sumy regions.

The Russian Defense Ministry also claimed that its troops have retaken the village of Robotnye in the southern Zaporizhzhia region. Ukrainian forces had gained control of the village last August in what was seen as an important advance in a counteroffensive that eventually petered out.

Elsewhere in Ukraine’s southern regions, an aerial attack on the central district of Kherson wounded 17 civilians, the regional prosecutor’s office said. And a Russian missile attack injured six people in Mykolaiv, according to Ukraine’s rescue service.