Thousands of protesters remain in a tense standoff with police on Kyiv's Independence Square, which has been the epicenter of antigovernment protests that began three months ago.
Ukraine President Viktor Yanukovych and opposition leaders have agreed to "a truce" and the start of direct negotiations on ending the country's crisis.
Yanukovych made the announcement on his presidential website after talks on February 19 in Kyiv with the three main opposition leaders.
Opposition leader Arseniy Yatsenyuk -- who took part in the meeting -- said in a statement on the website of his Batkivshchyna party: "The storming of the Maidan (Independence Square) which the authorities had planned today will not take place."
At least 26 people have been killed this week in the worst bloodshed since protests erupted against Yanukovych last November.
The announced truce comes ahead of a special EU meeting on Ukraine later on February 20 in Brussels.
The foreign ministers of France, Poland, and Germany will travel to Kyiv ahead of that meeting to meet with government and opposition officials before returning to Brussels later in the day.
U.S. President Barack Obama cautiously welcomed news of the truce while on a visit to Mexico.
"We've obviously seen reports about a truce between the government and opposition. If the truce is implemented it could provide space for the sides to resolve their disagreements peacefully," Obama said.
"And going forward, we will continue to do whatever we can to support Ukrainians as they seek a peaceful solution and respond to the aspirations of the Ukrainian people for a strong, unified democracy that is fully integrated into the international community."
Visa Ban
Earlier, a State Department official announced a U.S. visa ban on 20 senior Ukrainian officials and warned of more action in concert with the EU if the violence in Ukraine continues.
Meanwhile, a tense calm was reported overnight on the streets of Kyiv as thousands of protesters remain on Independence Square, or the Maidan.
NATO leaders urged Ukraine's armed forces to stay out of the crisis there, warning Kyiv that its relations with the Western alliance would suffer if the military did intervene.
"I strongly urge the Ukrainian government to refrain from further violence. If the military intervenes against the opposition, Ukraine's ties with NATO will be seriously damaged," NATO Secretary-General Anders Fogh Rasmussen said in a statement.
WATCH: Fires Burn On Kyiv's Indpendence Square After A Night Of Violent Clashes
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After Night Of Clashes, Fires Burn On Kyiv's Independence Square
Earlier on February 19, President Viktor Yanukovych sacked the head of the Ukrainian armed forces.
Yanukovych said he had dismissed Volodymyr Zamana as chief of the general staff and commander of the armed forces, and replaced him with Yuriy Ilyin, the naval chief.
The statement gave no reason for the move.
The dismissal came after the Ukrainian Defense Ministry said the armed forces could participate in a nationwide "antiterrorist" operation being prepared by the Security Service.
Annoucing preparations for a counterterrorism campaign, Ukrainian Security Service head Oleksandr Yakimenko said that over the past few days, some 1,500 firearms and 100,000 bullets had been taken from security forces and ended up in the hands of "criminals."
The latest upsurge in violence erupted just days after tensions appeared to ease somewhat after the government implemented a conditional amnesty for people who were detained since the antigovernment demonstrations began in November.
The antigovernment movement was triggered by Yanukovych's decision last November not to sign cooperation accords with the European Union and instead accept a $15 billion bailout from Russia.
