(CBS) — Tensions in the Ukraine are rising both on land and on sea. The ripples continue to be felt in Chicago.

Russian President Vladmir Putin showed no signs of backing down Monday, as Russian soldiers in Crimea reportedly sent a deadline to Ukraine to surrender or face assault.

President Obama met Monday with Israel’s prime minister and warned Putin against an all-out invasion.

A wider assault is exactly what Northwestern University Prof. Yohanan Petrovsy-Shtern, an expert on Eastern Europe, now believes is imminent.

“It is extremely dangerous to allow him to swallow Crimea, because it is feeding the crocodile with little pieces. You only ignite the appetite of the crocodile,” he tells CBS 2’s Derrick Blakley.

Meanwhile, Ukrainian-Americans in Chicago were stunned by the latest developments.

“Literally within a week of becoming a new nation, to have an invasion on our hands is extremely disheartening and scary,” Alla Dziuma tells CBS 2’s Mike Parker.

Dziuma knows first-hand what went into the struggle in the streets that created that new nation. She was in those streets herself in January.

Dziuma and physician Mariya Dmitriv are helping to run an internet campaign aimed at raising money for medical supplies and assistance to those injured and wounded in the revolt.

“We have to protect each other, we have to help each other before it’s too late,” Dmitriv says.

U.S. intelligence estimates another 5,000 Russian troops have joined the 15,000 in the Crimea since the crisis began last week. But thousands more are massed on the Russian side of the Ukraine border as Ukraine’s under-manned military mobilizes to fight a possible wider invasion.

U.S. Secretary of State John Kerry is travelling to Ukraine for talks with its new government tomorrow.

Petrovsky-Sthern says time is running short.

“It has to be an immediate diplomatic sanction. It has to be an immediate, very strong, exhortation on the political level, and it has to be an immediate economic message,” he says of the response that is needed.

The Ukraine crisis is being debated right now in the U.N. Security Council.

The Russian ambassador claims the former Ukrainian president, who fled to Russia, requested Moscow’s military intervention.

Little concrete action is expected from the U.N. because Russia could veto any sanctions.