Russia-Ukraine updates: Putin says 'certain positive movements' in negotiations

The State Department spoke out against the Kremlin's allegations of U.S. chemical or biological weapons activity in Ukraine.

"Russia has a track record of accusing the West of the very crimes that Russia itself is perpetrating," State Department spokesperson Ned Price said in a statement Wednesday, calling the allegations of U.S. biological weapons labs and chemical weapons development in Ukraine "outright lies," "conspiracy theories," "disinformation" and "total nonsense."

"Russia is inventing false pretexts in an attempt to justify its own horrific actions in Ukraine," he continued. "The United States does not own or operate any chemical or biological laboratories in Ukraine, it is in full compliance with its obligations under the Chemical Weapons Convention and Biological Weapons Convention, and it does not develop or possess such weapons anywhere."

-ABC News' Conor Finnegan

House Speaker Nancy Pelosi, D-Calif., said Ukrainian President Volodymyr Zelenskyy reiterated that his country needs aircraft in order to continue its resistance from the Russian invasion.

"He wants planes. He wants anti-missile weaponry. He wants armored cars ... tanks," Pelosi said of the 45-minute call on Wednesday. "He wants the planes, the planes, the planes."

It was not clear whether Pelosi was aware of the Pentagon’s statement rejecting a plan from Poland to provide Soviet jets to Ukraine in exchange for newer American replacements. She also continued to dim the prospects of the U.S. instituting a "no-fly" zone.

"He also said that we're going to need everybody's help rebuilding Ukraine," Pelosi said.

-ABC News' Lalee Ibssa, Benjamin Siegel and Rachel Scott

Ukraine has evacuated about 40,000 people in the last 24 hours, but most of the agreed-upon humanitarian corridors in six cities in Ukraine are still not holding, Ukrainian presidential adviser David Arakhmia said Wednesday.

Officials had hoped to move at least 100,000 women and children out of the country in that time frame but were not able to because the corridors were not clear, he said.

The northern city of Sumy was again the only place where a substantial evacuation was able to take place, with local authorities estimating 20,000 people left Wednesday.

An evacuation column was also able to bring people out of Energodar, the city that is home to the nuclear power station attacked last week, taking them to Zaporizhzhia.

An evacuation attempt from the besieged city of Mariupol again had to be abandoned, while in the region north of Kyiv, 50 buses attempting to evacuate people via a new humanitarian corridor became trapped after Russia forces blocked them. It was unclear whether those buses were eventually permitted to continue on to Kyiv. Some people, including 50 children, were evacuated today.

About 250 people were evacuated from the northeastern town of Izyum near Kharkiv, the advisor said.

Ukrainian President Volodymyr Zelenskyy said humanitarian corridors have again been agreed upon with temporary cease-fires for Thursday.

Russia could use chemical or biological warfare as it escalates its attack on Ukraine, White House press secretary Jen Psaki said in a statement to ABC News Wednesday.

"We should all be on the lookout for Russia to possibly use chemical or biological weapons in Ukraine, or to create a false flag operation using them," Psaki said. "It’s a clear pattern, and no one should fall for it."

Psaki prefaced that statement by noting false claims from Russia, endorsed by China, "about alleged U.S. biological weapons labs and chemical weapons development in Ukraine," calling those accusations "preposterous."

"It’s exactly the kind of disinformation operation we’ve seen repeatedly from the Russians over the years in Ukraine and in other countries around the world, which have been debunked conclusively, and an example of the types of false pretexts we have been warning the Russians would invent," she said.

The U.S. is in "full compliance" with its obligations under the Chemical Weapons Convention and the Biological Weapons Convention and "does not develop or possess such weapons anywhere," Psaki said.

-ABC News' Justin Gomez