US surveillance data crucial for Ukraine, top commander says

NORTHERN UKRAINE -- Lt. Gen. Serhiy Nayev, one of the most senior commanders of the Ukrainian Armed Forces, believes that the data surveillance the United States has collected is crucial in Ukraine's efforts amid the ongoing war.

Nayev is in charge of all troops based in the north of Ukraine which guard 600 miles of border with Belarus and Russia. In an exclusive interview with ABC News, he gave rare on-camera details about intelligence provided by the U.S., which has allowed the Ukrainian military to destroy key Russian targets in occupied parts of Ukraine.

The Ukrainian commander confirmed that the U.S. provides "surveillance data," allowing the Ukrainian Armed Forces to more accurately pinpoint Russian targets within Ukraine's borders.

"This help is crucial for us," he told ABC News.

Nayev said he was in "constant contact" with American generals stationed in other parts of Europe.

He said an exchange of data between the Ukrainians and Americans helped the Ukrainian military to pinpoint targets using U.S.-supplied HIMARS rocket systems.

"This work goes perfectly in real-time," he said.

Nayev spoke with ABC News at a series of Ukrainian military exercises held Saturday in the Rivne region of northern Ukraine, approximately 40 miles south of the border with Belarus.

During the military exercises, Ukrainian forces simulated how they would defend a major nuclear power plant situated in that region in the event of a fresh Russian invasion from the north.

When Russia launched its full-scale invasion of Ukraine in February of last year, Russian troops quickly seized the Zaporizhzhia Nuclear Power Plant in southern Ukraine.

Russia's control of the Zaporizhzhia Nuclear Plant presents a high-stakes challenge for Ukrainian forces in that part of the country and the Kremlin has often made ominous warnings about the potential for a wartime nuclear disaster at the plant.

Nayev said Ukraine had a "good understanding" of the threat of a Russian assault from the north, underlining that Ukrainian forces are "not just waiting for them."

"This is the toughest phase of war because the enemy strengthened its forces thanks to new mobilization and their forces are much bigger now," Nayev said. "If we compare the beginning of the war, the number of their infantry troops was around 160,000-180,000 people. Now, it is more than 350,000. Their forces are much bigger and it makes the combat situation more difficult because of the larger number of men."

He said Ukraine had increased the number of land mines in the border region by tenfold.

However, the overall commander of Ukrainian forces in the north played down the likelihood of a Russian assault from Belarus in the near term.

Nayev also stressed the need for western partners to supply Ukraine with longer-range missiles so that Ukraine can hit Russian ammunition depots and military command and control centers in eastern and southern Ukraine.