Ukrainian President dissolves parliament, schedules elections

Also Monday, Russian Foreign Minister Sergey Lavrov didn't rule out that Russian President Vladimir Putin might have a direct meeting with Poroshenko when the two attend a trade meeting in Belarus on Tuesday.

"Russia is ready to take part in the Ukrainian crisis settlement in any format that might lead to their national unity," he added.

Lavrov told reporters that Russia hopes to send a second humanitarian aid convoy to Ukraine this week.

"Russia has notified the Ukrainian foreign ministry of its intention," he said.

Last week, a convoy of Russian trucks crossed that country's border into eastern Ukraine without Kiev's authorization.

In total, 227 vehicles were sent into territories held by pro-Russian rebels on Friday, according to the Organization for Security and Co-operation in Europe, which has an observer mission at the checkpoint the convoy went through. They all had returned to Russia by Saturday afternoon.

Russia said the vehicles were on an essential humanitarian mission and that it was satisfied with the deliveries, but international powers condemned it as a violation of Ukraine's sovereignty.

Officials in Kiev referred to it as an invasion.

The U.S. State Department expressed concern over news of a possible second convoy.

"Any new missions done without the explicit permission of Ukraine would be another provocative measure that would only escalate a situation President Putin claims he wants to resolve," spokeswoman Jen Psaki told reporters. "So, you can't say one thing and do another and expect the international community to believe that there is legitimate or credible intentions behind your words.'