KYIV, Ukraine >> NATO chief Jens Stoltenberg defiantly declared Thursday that Ukraine’s “rightful place” is in the military alliance and pledged more support for the country on his first visit to Kyiv since Russia’s invasion just over a year ago.

Ukrainian President Volodymyr Zelenskyy urged Stoltenberg, who has been instrumental in marshaling support from NATO members, to push for even more from them, including warplanes, artillery and armored equipment.

The Kremlin has given various justifications for going to war, but repeated Thursday that preventing Ukraine from joining NATO is still a key goal of its invasion, arguing that Kyiv’s membership in the alliance would pose an existential threat to Russia.

NATO leaders said in 2008 that Ukraine would join the alliance one day, and Stoltenberg has repeated that promise throughout the war, though the organization has established no pathway or timetable for membership.

“Let me be clear, Ukraine’s rightful place is in the Euro-Atlantic family,” Stoltenberg told a news conference. “Ukraine’s rightful place is in NATO.”

Zelenskyy said he was grateful for an invitation to a NATO summit in July in Vilnius, Lithuania, but said his country needs a roadmap for becoming a member.

“The time has come for the (alliance’s) leaders to define the prospects of Ukraine’s acquisition of NATO membership, to define the algorithm of Ukraine’s movement towards this goal, and to define security guarantees for our state for the period of such movement — that is, for the period before NATO membership,” he said.

Stoltenberg said he and Zelenskyy discussed a NATO support program for Ukraine.

“This will help you transition from Soviet-era equipment and doctrines to NATO standards and ensure full interoperability with the alliance,” Stoltenberg said. “NATO stands with you today, tomorrow and for as long as it takes.”

He noted an announcement Thursday by Denmark and the Netherlands that they plan to provide Ukraine with at least another 14 refurbished Leopard 2 battle tanks by early 2024.

He added that he expected countries to “make new announcements of concrete military support to Ukraine” at a meeting Friday in Germany.

In other developments, a large explosion hit the Russian city of Belgorod late Thursday, and the Defense Ministry said one of its Su-34 warplanes accidentally discharged ammunition over the city about 25 kilometers (15 miles) from the Ukrainian border. The government gave no further details.

Belgorod regional Gov. Vyacheslav Gladkov said the blast injured at least two people, damaged homes and left a crater about 20 meters (65 feet) across.

The fighting in recent months has become a war of attrition, with neither side able to gain momentum. But Ukraine has recently received sophisticated weapons from its Western allies and is expected to launch a counteroffensive in coming weeks.

Russian President Vladimir Putin has warned that Moscow could use “all means available” — a phrase some see as a threat to use nuclear weapons — in response to an attack on its territory if Ukraine attempts to recapture Moscow-occupied areas.

NATO has no official presence in Ukraine and provides only nonlethal support to Kyiv, but Stoltenberg has been the strong voice of the alliance throughout the war.

A procession of international leaders has made the journey to Kyiv over the last year, and the former Norwegian prime minister is one of the last major Western figures to do so.

NATO, formed to counter the Soviet Union, has long feared being dragged into a wide war with nuclear-armed Russia. But as the West has moved from hesitantly providing helmets and uniforms to tanks, warplanes and advanced missile systems, high-level visits have become routine.

Kremlin spokesman Dmitry Peskov said Thursday that preventing Ukraine from joining NATO remains one of the goals of what Moscow calls its “special military operation.” Speaking in a conference call with reporters, Peskov said that Ukraine’s accession would pose a “serious, significant threat to our country, to our country’s security.”

Earlier this month, Finland joined the alliance, setting aside decades of neutrality in a historic realignment of Europe’s post-Cold War security landscape. While NATO says it poses no threat to Russia, the Nordic country’s accession dealt a major political blow to Putin.

Finland’s membership doubles Russia’s border with the world’s biggest security alliance. Neighboring Sweden is expected to join too, possibly by the time U.S. President Joe Biden and his NATO counterparts meet in Vilnius in July.

The alliance has focused on bolstering defenses on its own territory to dissuade Putin from attacking any member country. Under NATO’s collective security guarantee, an attack on one member country is considered an attack on all of them.

On Friday, Stoltenberg will attend a meeting of the Ukraine Defense Contact Group at Ramstein Air Base in Germany with U.S. Defense Secretary Lloyd Austin. The group is the main international forum for drumming up military support for Ukraine.

Meanwhile, the Ukraine Space Agency said Thursday that a bright flash of light in the night sky over the country the previous day was probably a meteor entering the atmosphere. Residents of the capital and several cities in Belarus saw the flash of light, which lingered for a couple of seconds, and an explosion was heard in the Kyiv region. It triggered an air raid alarm in Kyiv.

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Cook reported from Brussels.