Kiev, Ukraine (CNN) Russian leaders must be blind if they keep denying that forces from their country have crossed the border, Ukraine's prime minister said Thursday.

"If they need, I can give them my glasses," Prime Minister Arseniy Yatsenyuk said, removing black frames from his face and holding them up to reporters.

"It is crystal clear that (the) Russian military is on the ground," he said, as U.S. Secretary of State John Kerry stood by his side.

"We are not fighting so-called rebels or guerrillas," Yatsenyuk said. "We are fighting with the Russian regular army."

Ukraine Prime Minister Arseniy Yatsenyuk, in Kiev with U.S. Secretary of State John Kerry, offers his glasses to Russian President Vladimir Putin.

It's an argument he's made before, but now the timing is key.

Kerry visited Ukraine Thursday in the midst of what State Department officials called a grave escalation on the ground as the conflict between Ukrainian forces and pro-Russian separatists claims a growing number of lives. Both sides in the conflict have been blamed for shelling civilian areas.

Kerry didn't mince words Thursday about who he believes is responsible for the bloodshed.

"Let there be no doubt about who is blocking the prospect of peace here. ... Russia, with impunity, seemingly, has acted to cross that border at will with weapons, with personnel, with the instruments of death that they are bringing into Ukraine," he said. "Russia and the separatists are seizing more territory and continuing to refuse control to Ukraine of its rights as a sovereign nation."

Major questions loom as a solution to surging violence and escalating problems remains elusive: Will leaders strike a new ceasefire deal? Will the United States give Ukraine weapons to help defend its territory? And what's next for civilians caught in the crossfire?

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'No Russian tanks'

Kerry called on Russia to take three steps he said would enable a diplomatic solution "that is staring everyone in the face."

Those are: pulling back heavy weapons beyond the range of civilian populations, removing foreign troops and heavy equipment from Ukraine, and closing the Russia-Ukraine border.

A spokesman for Putin, Dmitry Peskov, told CNN that Kerry's remarks in Ukraine "just shows the unwillingness and inability of the United States to participate in settlement of the Ukrainian crisis."

"As for Russian tanks, allegedly crossing Russian-Ukrainian border, we've commented on this before -- there are no Russian tanks or army in Ukraine, such accusations are not true," he said.

Peskov called the upcoming meeting between Putin, Merkel and Hollande "a positive step in settlement of the Ukrainian crisis."

Hollande said they would push a joint proposal for new negotiations that would be "based upon the territorial integrity of Ukraine."

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New NATO teams near Russia's border

With tensions on the rise, there's another player in the mix: NATO is stepping up its presence close to Russia's western border.

Defense ministers decided Thursday to establish new NATO command and control units in Estonia, Latvia, Lithuania, Romania, Bulgaria and Poland.

Each team will have 40 to 50 staff officers, half of them locals, in order to improve NATO training and facilities in each country.

"These units will make it easier to deploy NATO forces rapidly," NATO Secretary General Jens Stoltenberg said.

Russia is unlikely to welcome the prospect of more NATO forces stationed nearby.

Putin last month called the Ukrainian army "a NATO legion" that has the geopolitical goal of containing Russia rather than defending Ukraine's national interests, according to Russia's state-run Tass news agency.

Ukraine is not a NATO member. But Stoltenberg told reporters that NATO "strongly supports Ukraine" and is bolstering forces in its eastern member states in response to a "pattern" of behavior. Russia, he said, has already violated the territorial integrity of Georgia, Moldova and Ukraine.

Stoltenberg said he would hold bilateral meetings in Munich, Germany, this weekend with Kerry, U.S. Vice President Joe Biden, Poroshenko and Russian Foreign Minister Sergey Lavrov.

'Defensive lethal aid'

The European Union and United States have already imposed a series of financial sanctions targeting Russian interests and separatist leaders in Ukraine.

The United States has steered clear of sending military aid. But that could change, officials said this week, noting that the United States is now considering sending aid to help the Ukrainian government fend off attacks from pro-Russian rebels in the eastern part of Ukraine. This assistance would come in the form of so-called defensive lethal aid, which could include anti-tank, anti-air and anti-mortar systems.

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Asked if France would join the United States in providing such equipment to the Ukrainian military, Hollande said "the option of negotiation, of diplomacy, cannot be extended indefinitely."

But the French President emphasized that first, he and Merkel are working toward a proposal they hope will be acceptable to all parties in the conflict.

"We want to develop a German and French negotiation document, along with Ukraine and also with Putin," he said.

"If we succeed, we will have avoided an escalation of the conflict. If we fail, and this hypothesis remains, what will be said? That France and Germany will have done everything they could do to take action to resolve the conflict."

Help for civilians

Over the past few weeks, fighting has intensified in eastern Ukraine, particularly in the Donetsk region.

Civilians increasingly are falling victim, with at least 224 killed and more than 540 injured in the final three weeks of January, the U.N. High Commissioner for Human Rights said Tuesday.

Eight civilians were killed and 33 injured as the result of shelling in Donetsk city in the past 24 hours, the city's official website said Thursday. Five Ukrainian soldiers were killed and 28 injured in the same time period, the Ukrainian military said.

Kerry announced Thursday that the U.S. government will provide $16.4 million in new humanitarian aid to help Ukrainians affected by the violence.

"The funding will be used to support the Ukrainian government's response to the crisis caused by Russia's aggressive actions and will also help alleviate the suffering of people in conflict-affected areas of eastern Ukraine," the State Department said.

"Many of these people are extremely vulnerable and unable to leave."