(CNN) The European Union announced plans Wednesday for 700 million euros ($760 million) in emergency aid to Greece as the economically struggling country copes with an influx of migrants stranded in hopes of gaining entry into Europe.

The EU's Christos Stylianides revealed the emergency funding proposal, promising to "fast-track" the assistance. But EU member states must still approve the funding.

"These are extraordinary times," said Stylianides, European commissioner for humanitarian aid and crisis management. "We all need to step up our efforts with no delay to prevent a further deterioration of the situation."

We proposed: EUR 700 ml for 3 yrs to cover basic necessities-food, shelter, clean water & emergency health care in overwhelmed Member States

Greece, the main gateway to Europe, had asked the EU for help to provide for tens of thousands of migrants in its territory.

A bottleneck of migrants has backed up rapidly in the wake of other European nations tightening border restrictions -- a development that led the U.N. High Commissioner for Refugees to warn Tuesday of a burgeoning humanitarian disaster.

The aid proposal -- intended to meet basic needs such as food, water and shelter over the next three years -- came a day after NATO's top general told a Pentagon briefing that ISIS was exploiting the migrant crisis.

Following testimony to the Senate Armed Services Committee, U.S. Air Force Gen. Philip Breedlove told reporters Tuesday that mass migration spurred by the ongoing conflict in Syria and the threat of ISIS in the Middle East was allowing terrorists free entry into Europe.

He warned that the mass influx of migrants is allowing ISIS to spread "like a cancer, taking advantage of paths of least resistance and threatening European nations, and our own, with terrorist attacks."

Breedlove, who is head of Supreme Allied Command in Europe, said the migration "masks the movement of criminals, terrorists and foreign fighters" into the continent.

U.N. agency warns of 'imminent humanitarian crisis'

Elsewhere Tuesday, the U.N. refugee agency warned the constant influx of migrants meant Europe faced "an imminent humanitarian crisis."

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More than 131,000 migrants entered Europe in the first two months of 2016 -- a number close to the total for the first half of 2015, according to the U.N. agency's figures. More than 1 million migrants entered Europe last year.

The failure to mount a unified response to the situation means Europe now faces a crisis "largely of its own making" as the buildup of migrants stranded in Greece grows rapidly, a statement said.

Some European countries, including those along the main Balkan migration route through the continent, recently agreed to tighten border controls to slow arrivals to a trickle.

The move has created a backlog of migrants in Greece, which faces its own severe financial hardships, as the flow of people there from Turkey continues unabated.

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Tensions boiled over Monday at Idomeni, a major transit camp on the Greece-Macedonia border, as migrants were denied permission to cross into Macedonia. Macedonian authorities have been letting a few hundred cross each day, but only Syrians and Iraqis with photo identification.

The U.N. refugee agency said the number of migrants stuck in Greece had soared to 24,000 by Monday night, with about 8,500 of them stuck at Idomeni.

Merkel: Reinstate Schengen system

Also Tuesday, German Chancellor Angela Merkel said European countries needed to reinstate the Schengen system of border-free travel within Europe to deal with the crisis rather than implement extra border controls.

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"The situation is not yet so that we can be content. Every day we see the pictures from Greece -- we have to get back to the Schengen system," Merkel said at a news conference with Croatian Prime Minister Tihomir Oreskovic.

Some member states have temporarily suspended 1985's Schengen Agreement, which has guaranteed free movement within Europe. It is expected to be amended later this month.

"Greece of course has to protect its borders -- this is not about only protecting the Greek-Macedonian border from the Macedonian side, so that we don't get new routes in the migration flow."

She also urged EU member states to stick to their obligation, made in September, to resettle 160,000 refugees among themselves over two years. So far, only hundreds have been resettled.

Rise of European Islamophobia

Rights groups have cautioned against scapegoating refugees after violence such as the deadly coordinated attacks in Paris in November.

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"Significant refugee flows to Europe, spurred largely by the Syrian conflict , coupled with broadening attacks on civilians in the name of the extremist group (ISIS), have led to growing fear-mongering and Islamophobia," Human Rights Watch said in its 2016 World Report

Breedlove told the Senate Armed Services Committee on Tuesday that alongside the threat posed by extremist organizations in Europe was the potential for unrest from local nationalists opposed to the unprecedented influx of refugees from Syria, Afghanistan, Iraq and unstable parts of Africa.

Fears are they could become increasingly violent, building on the small number of attacks against migrant and refugee populations.

Russia: Contributing to instability

In his Pentagon appearance, Breedlove also pointed a finger at a "resurgent, aggressive Russia ," which "poses a long-term and existential threat to the U.S. and our European allies."

Russia's involvement in the Syrian civil war, which Breedlove said had bolstered Syrian President Bashar al-Assad and his allies, has changed the dynamic and "complicated the problem ... in the air and on the ground."

The view is compounded by Pentagon reports that Russia is using the shaky ceasefire in Syria to seize key territory