President Vladimir Putin called his Ukrainian counterpart Petro Poroshenko a "partner" and said in a televised interview recorded Friday that they have agreed on Russia's next aid delivery.

Putin said that his meeting with Poroshenko for marathon talks this week "was very good, that was my impression. It was quite frank," according to an extract of an interview to air in full on Channel One television on Sunday evening.

Russian strongman Vladimir Putin first used "Novorossiya" -- the loaded Tsarist-era name for what is now southern and eastern Ukraine -- just after annexing Crimea from Ukraine in March, sparking outrage in Kiev.

The Kremlin made a reference to the term again on Friday when it released Putin's address to Ukraine's pro-Russian separatists, pointedly calling them defenders of "Novorossiya" (New Russia).

Germany warned Friday that the Ukraine crisis was spiraling "out of control", as European Union foreign ministers grappled with how to respond to what some termed a Russian invasion.

"The situation in Ukraine is entering a new dimension," German Foreign Minister Frank-Walter Steinmeier told reporters on the sidelines of talks with his EU counterparts in Milan.

Polish Foreign Minister Radoslaw Sikorski on Friday described the fighting in neighboring Ukraine as a "war", as the West accused Moscow of direct involvement in the escalating conflict.

"If it looks like a war, sounds like a war and kills like a war, it is a war," Sikorski wrote on Twitter about the now four-month conflict between government troops and pro-Moscow rebels.

The forces of the Russian-led CSTO military alliance are ready if needed for a peacekeeping operation, a senior official said Friday, as pro-Kremlin fighters were beating back Kiev's troops in eastern Ukraine.

NATO warned Russia on Friday over what it described as a "blatant violation" of Ukraine's sovereignty after the West accused Moscow of direct involvement in the escalating conflict.

Fears of a wider confrontation have spiraled after NATO said Russia had sent troops to fight in Ukraine and funneled huge amounts of heavy weaponry to pro-Kremlin rebels in what Kiev branded an invasion.

U.N. Secretary General Ban Ki-moon on Friday expressed grave concerns about the intensifying conflict in Ukraine after Kiev and the West said Russian troops were actively involved in fighting in the country's east.

Sitting beside a trench, the smoke of nearby combat visible, "Batya" looks towards the besieged town of Ilovaysk and considers the options of the pro-Kiev fighters there battling for survival.

Russian President Vladimir Putin has called on pro-Moscow separatists in Ukraine to open a "humanitarian corridor" to allow Ukrainian troops to escape from the rebel-held eastern town of Novoazovsk.

"I call on the rebel forces to open a humanitarian corridor for the Ukrainian troops who are surrounded, so as to avoid unnecessary casualties and to give them the opportunity to withdraw from the zone of operations," Putin said in a statement issued overnight Thursday.

The United States warned Thursday it was considering new sanctions against Russia over its involvement in the latest fighting in Ukraine.

"We have additional tools and sanctions that we can certainly choose to put in place," State Department spokeswoman Jen Psaki said, who said those options would be discussed with NATO allies.