Russia-Ukraine updates: Russian missiles hit close to nuclear reactors: IAEA director

U.S. Secretary of State Antony Blinken on Monday condemned the conduct of Russian troops around the Zaporizhia power plant -- the biggest nuclear power plant in Ukraine and Europe -- calling it “the height of irresponsibility."

Speaking after nuclear nonproliferation talks at the United Nations in New York, Blinken said Russia was turning the power plant into a “nuclear shield."

“Russia is now using the plant as a military base to fire at Ukrainians, knowing that they can’t and won’t shoot back because they might accidentally strike a nuclear reactor or highly radioactive waste in storage,” Blinken said.

The secretary added that Russia's actions bring “the notion of having a human shield to an entirely different and horrific level.”

Russia was already accused of firing shells dangerously close to the Zaporizhzhia nuclear power plant in March as Russian troops occupied the facility in the first weeks of the invasion of Ukraine.

Russian President Vladimir Putin said on Monday a nuclear war should “never be unleashed,” according to local media. Putin stressed that Russia continues to fulfill its obligations under the Treaty on the Non-Proliferation of Nuclear Weapons, as well as its bilateral agreements with the U.S. on the reduction of nuclear weapons.

-ABC News' Edward Szekeres, Yulia Drozd, Max Uzol and Fidel Pavlenko

The United States is sending a 17th round of aid to Ukraine, consisting of more ammunition for HIMARS rocket systems and howitzers, White House spokesman John Kirby announced.

This aid comes from presidential drawdown authority, separate from any aid passed by Congress.

This package totals $550 million and brings the total of U.S. presidential drawdown aid given to Ukraine since February to $8.8 billion.

-ABC News’ Luis Martinez and Sarah Kolinovsky

The Ukrainian Armed Forces said on Monday Russian troops were massing in the direction of the town of Kryvyi Rih in the Dnipropetrovsk region, possibly in a bid to prepare for a large Ukrainian counterattack.

Talk of a major Ukrainian counteroffensive aimed at taking back the southern city of Kherson, about 140 miles south of Kryvyi Rih, has been gathering pace for several weeks.

The Ukrainian military also issued the maximum missile-fire-threat alert on Sunday in reaction to Russian troops massing in the Black Sea.

At least 17 warships and boats of the Russian Black Sea fleet were maneuvering near the Crimean coast on Sunday, according to Ukrainian military officials.

Among them were six Kalibr cruise missile carriers with more than 40 high-precision missiles on board, as well as four large landing ships.

Russia has also been transferring a large number of troops to occupied Crimea, Vadym Skibitskyi, of the Ukrainian Ministry of Defense, said on Monday.

Russia plans to deploy these troops in the south of Ukraine to conduct future combat operations, Skibitskyi said.

The official added that Russia withdrew tactical groups of airborne troops from the eastern Donetsk region and transferred them to occupied Kherson about two weeks ago.

Russian forces have resumed localized ground attacks northwest and southwest of Izyum over the weekend and may be setting conditions for offensive operations further west into Kharkiv Oblast or toward Kharkiv City, the Institute for the Study of War said in its latest report.

-ABC News' Edward Szekeres, Yulia Drozd and Max Uzol

Ukrainian Minister of Foreign Affairs Dmytro Kuleba called Monday a "day of relief for the world" as his country resumed grain shipments for the first time since Russia's offensive began.

"The day of relief for the world, especially for our friends in the Middle East, Asia, and Africa, as the first Ukrainian grain leaves Odesa after months of Russian blockade," Kuleba wrote in a post on Twitter. "Ukraine has always been a reliable partner and will remain one should Russia respect its part of the deal."