The next 24 hours are "vital" for Ukraine as its resistance prepares for renewed pressure.

• In the next 24 hours, Ukraine's president, Volodymyr Zelenskyy, believes his country will face a critical juncture.
• Russian forces are still being fought by Ukrainian troops and armed citizens.
• Sanctions have been imposed on Russia, isolating its economy and financial system.

In the next 24 hours, Ukraine's president, Volodymyr Zelenskyy, believes that his country's Ukrainian troops and armed citizens will continue to fight against invading Russian forces, making it a crucial period for Ukraine.

When speaking to Boris Johnson on Sunday evening, Zelenskyy made a comment about the bravery of the Ukrainian people. He also praised Zelenskyy's leadership "in the face of such adversity," the British government said in a statement.

Russian forces are attacking Ukraine's major cities from the north, east, and south, with both ground and air assaults causing damage and loss of life.

On Sunday night, explosions were heard in Kharkiv and Kyiv, prompting the lifting of the two-day curfew in Kyiv on Monday morning, allowing residents to leave the city.

Since the attack began early last Thursday, Russia's forces have not made the advances they expected against Ukraine's armed forces and volunteer fighters, who have put up a strong defense.

The Belarus factor?

Belarus may deploy its troops to support Russia, putting pressure on Ukraine's resistance, according to fears. CNBC has reached out to the Belarusian Defense Ministry for comment.

Belarus may host Russian nuclear weapons following a constitutional referendum that approved the country's renunciation of its non-nuclear status.

Belarus' support for Russia is viewed as another move in backing its ally, following Putin's decision to put Russia's nuclear deterrence forces on high alert amid global condemnation of the invasion.

Lukashenko, the president of Belarus, stated on Sunday that if the West transfers nuclear weapons to Poland or Lithuania, he will turn to Putin to return the nuclear weapons he previously gave away without any conditions.

Belarus has invited Ukrainian and Russian officials to peace talks, despite Lukashenko's threatening rhetoric. The exact date of the discussions is yet to be determined, but a Ukrainian president's office spokesperson announced on Monday that a delegation had arrived at the border with Belarus to engage in talks with Russian officials.

In a video on Sunday, Zelenskyy stated that he had little faith in the success of the negotiations, but was open to giving it a try; he said, "I will say honestly, as always, I do not really believe in the result of this meeting, but let them try."

What’s the situation in Ukraine?

The conflict's chaotic and unpredictable nature makes it challenging to determine the exact number of Ukrainian and Russian casualties. Reports from Ukraine suggest that hundreds of civilians, including children, have been killed. Additionally, Ukraine claims that thousands of Russian soldiers have been killed.

Russia has not disclosed the number of casualties, but its Defense Ministry stated on Sunday that "Russian military personnel have been killed and injured," according to the BBC report; Russia asserted that its losses were "several times less" than the number of "exterminated" Ukrainians.

On Monday, the U.K.'s Ministry of Defense released an update stating that the majority of Putin's ground forces are still more than 30km away from Kyiv, with their advance slowed by Ukrainian forces defending the Hostomel airfield, a crucial objective for the first day of the conflict.

Despite ongoing heavy fighting in Chernihiv and Kharkiv, both cities remain under Ukrainian control. Logistical failures and strong Ukrainian resistance continue to hinder the Russian advance on a broader scale.

Russia is facing increasing pressure from the West as it continues to invade Ukraine. The U.S., Europe, and Canada have agreed to impose sanctions on Russia, including removing key Russian banks from the SWIFT interbank messaging system and sanctioning its central bank. Additionally, the U.K. and EU have closed their airspace to Russian aircraft in an effort to isolate Russia further.