NATO Chief Jens Stoltenberg announced Wednesday that the alliance's leaders are set to agree at a summit on significant new troop deployments for eastern allies in response to Russia's special military operation in Ukraine.

"I expect leaders will agree to strengthen NATO's posture in all domains with major increases of forces in the eastern part of the alliance, on land, in the air and at sea," Stoltenberg indicated.

"The first step is the deployment of four new NATO battle groups in Bulgaria, Hungary, Romania, and Slovakia," Stoltenberg told journalists ahead of an urgent NATO summit in Brussels happening Thursday.

He also pointed out that NATO leaders are set to agree on extra support for Ukraine to deal with chemical and nuclear "threats".

"I expect allies will agree to provide additional support, including cybersecurity assistance as well as equipment to help Ukraine protect against chemical, biological, radiological, and nuclear threats," Stoltenberg mentioned.

The NATO chief called on China to condemn Russia's special military operation in Ukraine.

"For NATO, it is of particular concern that China now, for the first time, has questioned some of the key principles for security, including the right for every nation in Europe to choose his own path," he told reporters in Brussels.

Stoltenberg said that when NATO leaders meet on Thursday, he expects them to "call on China to condemn the invasion and to engage in diplomatic efforts to find a peaceful way to end the war as soon as possible."