Russian foreign minister Sergey Lavrov is scheduled to meet with Ukraine foreign minister Dmytro Kuleba in Antalya, Turkey, on Thursday, ahead of the start of the Antalya Diplomacy Forum.

This will be the first face-to-face high-level meetings between Russian and Ukrainian officials since the Russian invasion began.

This meeting is a continuation of the negotiating process "and a very important one," Kremlin spokesperson Dmitry Peskov said, according to Russian state-run news agency TASS.

Lavrov is expected to make a speech on Moscow's position on current issues in Antalya, and Turkish Foreign Minister Mevlut Cavusoglu is also scheduled to attend the meeting with Kuleba.

The third round of talks between Russian-Ukrainian delegates was held in Belarus on Monday.

-ABC News' Christine Theodorou

The head of the United Nations Children's Fund (UNICEF) strongly condemned a missile attack apparently launched by Russia Wednesday on a maternity hospital in Ukraine.

"I am horrified by the reported attack today on a maternity hospital in Mariupol, Ukraine -- an attack which reportedly left young children and women in labor buried beneath the rubble of destroyed buildings," UNICEF executive director Catherine Russell said in a statement. "We do not yet know the number of casualties but fear the worst."

A devastating airstrike destroyed a maternity and children’s hospital in the besieged southeastern Ukrainian city, causing multiple casualties. Ukraine’s president Volodymyr Zelenskyy and local officials posted videos on social media of the destroyed hospital.

Zelenskyy called the attack an "atrocity."

Russell said that if confirmed, the attack "underscores the horrific toll this war is exacting on Ukraine’s children and families."

"In less than two weeks, at least 37 children have been killed and 50 injured, while more than 1 million children have fled Ukraine to neighboring countries," Russell said.

Russell added, "Attacks against civilians and civilian infrastructure --including hospitals, water and sanitation systems and schools -- are unconscionable and must stop immediately. UNICEF renews its call for an immediate cease-fire and urges all parties to respect their obligations under international humanitarian law to protect children from harm, and to ensure that humanitarian actors can safely and quickly reach children in need. The children of Ukraine desperately need peace."

Russia has confirmed the use of thermobaric rockets, or vacuum bombs, the U.K. Ministry of Defense tweeted Wednesday.

The weapon uses a fuel container and two separate explosive charges to ignite a blast of extreme pressure and heat, creating a partial vacuum in an enclosed space.

The impact from the bomb is "devastating," according to the ministry.

-ABC News' Guy Davies

Papa John's and Heineken are the latest brands to cease business in Russia in response to the invasion of Ukraine.

The American pizza chain and the Dutch beer company join internationally known brands such as McDonald's, The Coca-Cola Company, PepsiCo and Starbucks in suspending operations in Russia.

While Heineken has stopped the production and sale of beer in Russia, Papa John’s has suspended all corporate operations there as well.

"It has ceased all operational, marketing and business support to, and engagement with, the Russian market, where all restaurants are owned by independent franchisees, and a master franchisee who controls operations and provides all supplies and ingredients for the restaurants through a supply chain that it owns and operates," a statement released Wednesday by Papa John’s read.

-ABC News' Victor Ordonez

The Russian forces charging toward Kyiv haven't made progress in the last day as they face Ukrainian resistance and low food and gas supply, a senior U.S. defense official told reporters Tuesday.

However, it could be a deliberate pause, the official said. "Part of the stall could be ... as a result of their own self-determined sort of pause in operations -- that they are possibly regrouping, rethinking, reevaluating," the official said.

The U.S. believes Russian forces "have committed now more than 80% of what was their pre-staged combat power," the official added.

The official said some Russian soldiers weren't told they were going into combat. The official said "not all of them were apparently fully trained and prepared."

The strong Ukrainian resistance has also hurt morale, according to the official.

Russia has now launched more than 400 missiles on Ukraine, the official said. The U.S. believes Russia has launchers that could be used for thermobaric weapons, but cannot confirm their use, the official said.

Russian forces are making the most progress in the south. Russians are attacking Kherson in south Ukraine, which "appears very much to be contested city at this point," the official said.

Russians are also approaching Mariupol in southeastern Ukraine, and while they haven't yet entered the city, "they are close enough now that they could attack Mariupol with long range fires," the official said.

Two towns on the path to Mariupol are believed to be occupied by the Russians, according to the official.

The U.S. believes the Russians hope to move north out of Mariupol up to the heavily-contested city of Kharkiv. The official said they believe Russian forces are trying to encircle Kharkiv.

The U.S. official noted that they've seen "certain risk-averse behavior by the Russian military" over the last week.

"Take the amphibious assault, for instance. They put those troops ashore a good 70 kilometers away from Mariupol because they knew Mariupol was going to be defended and they could put them ashore in an uncontested environment. And they still haven't reached Mariupol," the official said.

"They are not necessarily willing to take high risks with their own aircraft and their own pilots," the official said.

"And of course we're seeing that on the ground -- the fairly slow and steady progress that they have made, and you guys are seeing it for yourselves on the ground where ... units are surrendering, sometimes without a fight."

-ABC News' Matt Seyler