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

Russia's main objective in its invasion of Ukraine is still regime change in Kyiv and the dismantling of Ukrainian sovereignty, Russian Security Council Secretary Nikolai Patrushev suggested in a speech on Tuesday.

Patrushev said the Russian “military operation” in Ukraine will continue until Russia achieves its goals of protecting civilians from “genocide,” “denazifying” and demilitarizing Ukraine, according to the Institute for the Study of War (ISW).

The Russian official added that Ukraine must remain permanently neutral between Russia and NATO. Petrushev's remarks nearly mirrored the goals Russian President Vladimir Putin announced at the onset of the war to justify the military invasion.

Patrushev, a close Putin ally, repeated the Russian President's stated ambitions despite Russia's military setbacks in Ukraine and previous hints at a reduction in war aims following those defeats, the ISW pointed out.

Patrushev's explicit restatement of Putin's initial objectives “strongly indicates” that Russia does not consider its recent territorial gains in the Luhansk region to be sufficient, the ISW experts said.

Russia “has significant territorial aspirations beyond the Donbas” and “is preparing for a protracted war with the intention of taking much larger portions of Ukraine,” the observers added.

Patrushev's comments dampened hopes for a “compromise ceasefire or even peace based on limited additional Russian territorial gains,” the experts concluded.

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Max Uzol and Nataliia Kushnir

The town of Sloviansk in Donetsk Oblast will likely become the next "key" battleground in Russia's push to seize the Donbas region of eastern Ukraine, the U.K. Ministry of Defense said Wednesday in an intelligence update.

"Russian forces from the Eastern and Western Groups of Forces are likely now around 16 km north from the town of Sloviansk," the ministry said. "With the town also under threat from the Central and Southern Groups of Forces, there is a realistic possibility that the battle for Sloviansk will be the next key contest in the struggle for the Donbas."

In the meantime, Russian forces likely continue to consolidate control over the town of Lysychansk and the wider Luhansk Oblast, about 45 miles east of Sloviansk.

"To the north, it has committed most of the remaining available units from the Eastern and Western Groups of Forces to the Izium axis," the ministry added. "Over the last week, Russian forces have likely advanced up to another 5 km down the E40 main road from Izium, in the face of extremely determined Ukrainian resistance."

NATO announced on Monday it has concluded negotiations with Sweden and Finland on their accession to the organization.

"Finland and Sweden have completed accession negotiations at the NATO headquarters in Brussels, as agreed last week by the leaders of the countries at the summit in Madrid,” a NATO press release said.

“Both countries have officially confirmed their desire and ability to fulfill their political, legal and military obligations as NATO members," the NATO press service added.

The countries will sign their accession protocols on Tuesday. All member countries will then have to ratify the documents according to their national laws.

Finland and Sweden jointly submitted applications to join NATO on May 18, ending decades of neutrality in the face of Russia's invasion of Ukraine.

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Max Uzol and Nataliia Kushnir

Russian President Vladimir Putin celebrated the Russian seizure of Lysychansk and the majority of the Luhansk regional border in eastern Ukraine by appearing to direct his military to conduct an “operational pause”, the Institute for the Study of War reported on Monday.

Putin and Russian Defense Minister Sergey Shoigu called the recent Russian gains in the Luhansk region as a major victory for Russian forces in Ukraine.

The Russian president also stated that the Russian units that participated in the battle for Lysychansk should rest to increase their combat capabilities, the ISW report claimed.

Putin‘s public comment was likely meant to signal his concern for the welfare of his troops in the face of periodic complaints in Russia about the treatment of Russian soldiers, the ISW experts said.

Russian troops that fought through the Luhansk region are very likely in need of a significant period in which to rest and refit before resuming large-scale offensive operations, observers noted.

It is not clear, however, that the Russian military will accept the risks associated with a long enough operational pause to allow these likely exhausted forces to regain their strength, the ISW report said.

Putin was quick to remark on Monday that “other military formations, including the East Group and the West Group, must carry out their tasks according to the previously approved plans.”

“I hope that everything will happen … in the same way as it has happened in Luhansk,” the Russian President added as quoted by local media.

Vyacheslav Volodin, who chairs the Russian Duma -- the lower house of the Federal Assembly -- said on Tuesday that Ukraine was "doing everything" to ensure that Moscow's troops would not stop their "special military operation" at the borders of the self-proclaimed Donetsk People's Republic and Luhansk People's Republic in eastern Ukraine, according to Russian state media.

Serhii Haidai, the head of the Luhansk Regional Military Administration, said on Tuesday that Russian attacks in the Luhansk region destroyed more than 90% of the infrastructure in the territories that were actively defended by the Ukrainian military.

An overwhelming majority of houses were under fire, Haidai said, and most of them “can't be restored.”

-ABC News' Edward Szekeres, Yuriy Zaliznyak, Max Uzol and Nataliia Kushnir