U.S. Secretary of State Antony Blinken met with his Ukrainian counterpart, Dmytro Kuleba, spending about 45 minutes inside Ukraine’s Ministry of Foreign Affairs Thursday.

Prior to that, Blinken visited a children’s hospital in Kyiv where he met Patron, a bomb-sniffing Jack Russell terrier. The secretary presented Patron with treats and held him as they posed for a photo.

He also distributed stuffed animals to young patients present, including a 6-year-old girl, Maryna, who lost her leg and is learning to walk with a prosthetic.

This latest unannounced visit to Ukraine is the secretary’s fifth trip to the country and his third since the outbreak of the war. Blinken last visited Kyiv in late April. Blinken and Secretary of Defense Lloyd Austin remain the highest-level American officials to visit the country in the wake of Russia’s invasion.

-ABC News' Shannon Crawford

U.S. Secretary of State Antony Blinken arrived in Kyiv on Thursday for an unannounced visit to war-torn Ukraine.

His visit came on the heels of U.S. Secretary of Defense Lloyd Austin's announcement of a $675-million package of heavy weaponry, ammunition and armored vehicles for Ukraine amid Russia's ongoing invasion. In addition, Blinken announced Thursday that the Biden administration would provide a further $2 billion in long-term foreign military financing to Ukraine and 18 of its neighbors, including NATO members and regional security partners "most potentially at risk for future Russian aggression."

The United States will send another $675 million in assistance to Ukraine amid Russia's war, Secretary of Defense Lloyd Austin announced Thursday.

"Yesterday, President Biden approved the latest tranche of U.S. assistance to Ukraine, valued at up to $675 million, and this is the Biden administration's 20th drawdown of equipment from U.S. stocks for Ukraine since last August," Austin told reporters at the U.S. military's Ramstein Air Base in Germany, where he attended a meeting of the Ukraine Defense Contact Group.

"The latest package includes more GMLRS, 105 millimeter howitzers, artillery ammunition and HARMs, Humvees, armored ambulances, anti-tank systems, small arms and more," he added.

The Ukraine Defence Contact Group is a U.S.-led effort to bring together defense leaders from dozens of countries around the world in order to facilitate military support for Ukraine in its ongoing efforts to fight the Russian invasion. Austin said Thursday that the group was meeting to "renew our commitment and intensify our momentum to support the brave defenders of Ukraine for the long term."

"Today, four months after our initial Contact Group meeting, the war is at another key moment. Russian forces continue to cruelly bombard Ukrainian cities and civilians with missiles and artillery fire," he said. "But Ukrainian forces have begun their counteroffensive in the south of their country."

"This Contact Group needs to position itself to sustain Ukraine's brave defenders for the long haul," he added. "And that means a continued and determined flow of capability now."

Shelling on Tuesday damaged a backup power line at the Zaporizhzhia nuclear power plant in Ukraine, the United Nation's nuclear watchdog said Wednesday.

The International Atomic Energy Agency said there was no immediate impact from the damage because the Russian-held plant was already disconnected from the grid.

The plant previously lost all four of its regular power lines during the conflict, according to the IAEA.

The damaged power line is one of three backup lines between the plant and a nearby thermal power station. The other two are disconnected, the IAEA said.

In recent days, the plant has relied on its sole operating reactor for power, according to the IAEA, which stressed that a "secure off-site power supply from the grid and backup power supply systems are essential for ensuring nuclear safety and preventing a nuclear accident."

-ABC News' Jason Volack

U.S. President Joe Biden made an unannounced visit to war-torn Ukraine on Monday, arriving in Kyiv as Washington signals its ongoing support ahead of the one-year anniversary of Russia's invasion.

Biden's visit came ahead of a planned meeting with NATO allies in Poland. He is expected to give a speech at the Royal Castle Arcades in Warsaw on Tuesday evening to offer an appraisal of international support during the first year of the war and to address "how we will continue to stand with the people of Ukraine for as long as it takes," White House spokesperson Karine Jean-Pierre said in a statement earlier this month.

Biden also plans to meet in Poland with leaders of the Bucharest Nine, a group of eastern NATO allies formed in 2015 in response to Russia's annexation of Ukraine's Crimean Peninsula.

Ukrainian President Volodymyr Zelenskyy made a dramatic visit to the United States in December, his first known international trip since the Russian invasion began in February 2022. Zelenskyy met with Biden at the White House in Washington, D.C., before addressing members of U.S. Congress on Capitol Hill.