By Andrew Jay Rosenbaum

ANKARA

As Ukrainian government forces struggle to contain a powerful separatist offensive in the east of the country, the U.S. is expected to announce that it will deliver arms to Kiev.

The move has led to many observers asking the question: "Is this the start of a proxy war?"

A report -- released by a group of high-level analysts from the Brookings Institute, Atlantic Council and Chicago Council on Global Affairs -- based on discussions with NATO officials proposes that a significant level of support in arms and know-how will be provided by the international military organization.

Ukrainian President Petro Poroshenko said Wednesday he is "confident that the United States will agree to send weapons to his country to help it fight pro-Russian rebels."

For now, the war is going badly for Kiev.

'Inhumane conduct'

Government troops have been forced to abandon the main terminal at the Donetsk airport, while shelling attacks by pro-Russian separatists have pushed Ukrainian forces back at Mariupol, Donetsk and Debaltseve.

Shelling from both sides has caused numerous civilian casualties and, with bus stations and hospitals being targeted, the UN has issued a warning over inhumane conduct.

"The rebels are pressing their attacks, with about 3,000 troops and full heavy weapons support," explained the Ukrainian ambassador to Turkey, Sergei Korsunsky.

"Russia is now continuously supplying troops and weapons across the border," he said.

The object, the ambassador said, was "to force us into negotiations with the terrorists. That will not happen."

"Ukrainian forces will fight to push back these attacks on our country with all possible might," he added.

'Challenge to security'

U.S. Secretary of State John Kerry, due to visit Ukraine on Thursday, is expected to announce a provision of military aid to the hard-pressed country.

Kerry has said that he is "open" to the possibility of providing military aid, and the Pentagon now appears to support his view.

"A comprehensive approach is warranted, and we agree that defensive equipment and weapons should be part of that discussion." a Pentagon official said Wednesday.

According to U.S. officials, Russian success would fatally undermine Ukraine’s stability and embolden Kremlin to further challenge the security order in Europe.

The analysts' report said such an outcome could also tempt Russian President Vladimir Putin to use his argument of protecting ethnic Russians and Russian speakers to seek territorial changes elsewhere in the neighborhood, including in the Baltic States, provoking a direct challenge to NATO.

"Maintaining Western sanctions are critical but not by themselves sufficient. The West needs to bolster deterrence in Ukraine by raising the risks and costs to Russia of any renewed major offensive," it stated.

Lethal assistance

The report calls for $1 billion in military assistance in 2015,  followed by additional tranches of $1 billion in 2016 and also 2017.

Lethal defensive military assistance should include light anti-armor missiles, given the large numbers of armored vehicles that the Russians have deployed in Donetsk and Luhansk and the abysmal condition of the Ukrainian military’s light anti-armor weapons.

Additional non-lethal assistance should include radars, unmanned aerial vehicles, electronic counter-measures for use against opposing unmanned aerial vehicle (UAVs), secure communications capabilities, armored Humvees and medical support equipment.

Other NATO members should provide military assistance as well, the report concludes.

But will Kerry make all of these pledges on his visit?

"We think Kerry’s visit will be very important," Ambassador Korsunsky said.

Proxy war?

Russia has shipped a large number of heavy weapons to support the separatists in recent weeks, including T-80 and T-72 tanks, multiple-launch rocket systems, artillery and armored personnel carriers, western officials say.

So is Washington looking to beef-up Kiev’s stock of arms or perhaps launch a proxy war?

U.S. State Department spokeswoman Jen Psaki commented: “Well, I don't think anybody wants to get into a proxy war with Russia. And that is not the objective.

"Our objective here is to change the behavior of Russia. That’s the reason that we've put the sanctions in place. We certainly want to help Ukraine, a sovereign government, thrive and go through this transition period."

"No decisions have been made. I'm talking about the fact that we of course preserve the right to consider a range of options," she said, in an interview with a U.S. television station Tuesday.

But former Soviet leader Mikhail Gorbachev took a different view. "If we call a spade a spade, America has pulled us into a new Cold War, trying to openly implement its general idea of triumphalism. Where will it take us all?"

Civilians displaced

Putin has accused the West of trying to oust his regime -- an attitude which is not likely to brook increased opposition.

Meanwhile, the U.N. has raised the death toll from fighting in eastern Ukraine to more than 5,300 people since last April.

Another 1.5 million people have been displaced.

According to Russian-backed separatists in Donetsk, shelling in eastern Ukraine has killed at least eight people and wounded 22 others in the past day.

Ukraine said five more of its soldiers died Wednesday.

And with civilians in the war zones also being displaced from their homes by shelling, the prospect of cease-fire negotiations seems very far away.