Ukrainian President Volodymyr Zelensky said Wednesday, March 16 peace talks were beginning to "sound more realistic" — as he, along with U.S. and U.K. officials, reported Putin's offensive was stalling even as attacks on Kyiv and Mariupol were intensifying, Axios reports.

"Efforts are still needed, patience is needed," Zelensky said during a televised address as the invasion entered a third week.

"Any war ends with an agreement," added Zelensky, who thanked US. President Joe Biden "and all the friends of Ukraine" in the U.S. for a $13.6 billion aid package ahead of his congressional address Wednesday.

Ukrainian presidential aid Mykhailo Podolyak, a member of the peace talks delegation, tweeted that "fundamental contradictions" remained as peace talks with Russian officials were expected to continue Wednesday. "But there is certainly room for compromise," he added.

Loud explosions were reported in Kyiv on Wednesday morning. Kyiv entered a 35-hour curfew on Tuesday night, hours after at least four people were killed in a Russian airstrike on an apartment in Ukraine's capital.

Fresh attacks were also reported in Mariupol, where local officials said Russian forces had seized a hospital and took some 500 people hostage.