Ukrainian Interior Minister Arsen Avakov says force will be used if negotiations fail to remove separatists from regional government buildings in eastern Ukraine.
Avakov told journalists in Kyiv after a government meeting on April 9 that the situation will be resolved in the next two days.
He said there are two ways to solve the problem -- negotiations or force -- and "for the minority who want conflict, they will get a forceful answer from the Ukrainian authorities."
Hundreds of pro-Russia protesters stormed government buildings in Donetsk, Kharkiv, and Luhansk on April 6.
Separatists were expelled from the Kharkiv government building by Ukrainian special forces on April 8.
But protesters in Donetsk proclaimed the creation of a sovereign "people's republic" from within the regional government building on April 7 and have since built huge barricades around the structure.
Early on April 9, the Ukrainian Security Service (SBU) said more than 50 of the people who had been holed up in the occupied SBU headquarters in Luhansk had left.
Dozens of pro-Russia activists reportedly remain inside the heavily barricaded building in Luhansk.
An armed protester inside that SBU building told Reuters that those who left were not prepared to fight.
He said separatists who remain inside the heavily barricaded building were demanding that an independence referendum be held in Luhansk Oblast.
Serhiy Tihipko -- a presidential candidate who was a deputy prime minister in a government that served under ousted President Viktor Yanukovych -- met with the protesters in Luhansk and said he would discuss their demands with acting President Oleksandr Turchynov.
In Brussels, EU foreign-policy chief Catherine Ashton has said that she will meet with top U.S., Russian, and Ukrainian envoys next week to discuss the Ukraine crisis.
In a statement, Ashton said the meeting will involve U.S. Secretary of State John Kerry, Russian Foreign Minister Sergei Lavrov, and acting Ukrainian Foreign Minister Andriy Deshchytsya.
Russian President Vladimir Putin said at a government meeting on April 9 that he expected a "positive" outcome from the talks, but also warned Ukrainian leaders against doing "anything that can't be fixed
Earlier, Lavrov told Kerry that the four-way talks must focus on fostering dialogue among Ukrainians and not on bilateral relations among the participants.
The Russian Foreign Ministry said Lavrov spoke with Kerry by telephone twice on April 9, one day after Kerry accused Russian agents of stirring up unrest in eastern Ukraine.
In Washington, U.S. Assistant Secretary of State Victoria Nuland said on April 9 that Washington did "not have high expectations
" ahead of the talks.
But Nuland said Washington still believes that "it is very important to keep the diplomatic coor open."
Meanwhile, German Chancellor Angela Merkel said that Russia had failed to take steps to de-escalate the situation in Ukraine.
Merkel told parliament that it is difficult to see way in which Moscow is "easing tensions" in Ukraine.
She added that "Ukraine has...a right to choose its own path and we will insist on it."
The EU's confirmation of the meeting came soon after Kerry accused Russian agents and special forces of stirring separatist unrest in eastern Ukraine, saying Moscow could be trying to prepare for military action as it had in Crimea.
Kerry was testifying before a U.S. Senate panel in Washington on April 8.
"Everything that we've seen in the last 48 hours, from the Russian provocateurs and agents operating in eastern Ukraine, tells us that they've been sent there determined to create chaos," Kerry said.
Kerry called these efforts "illegal and illegitimate."
With reporting by Reuters, AFP, Interfax, and AP