The European Commission has unveiled a controversial plan for a European border guard agency that would deploy to member states overwhelmed by migrants — whether those nations want it or not.

The new agency would have a standing reserve force of at least 1,500 border guards that could be sent to EU border chokepoints within three days, rather than relying on time-consuming calls to nations for volunteers during emergencies.

"This is a safety net, which like all safety nets, we hope will never need to be used," European Commission Vice President Frans Timmermans told EU lawmakers on Tuesday.

The plan is contentious because it requires countries to surrender some of their sovereignty — something many have viscerally opposed so far — and it's unclear whether the scheme will win enough backing among the bloc's 28 members to pass. EU leaders will discuss it for the first time at a two-day summit beginning Thursday.

The proposal is just the start of a potentially long and divisive legislative process. Still, the EU has planned a 2016 budget for the agency of 238 million euros ($260 million).

According to the International Organization for Migration, more than 920,000 people have entered the EU so far this year. The influx has overwhelmed national border guards and reception capacities, notably in Greece, where some 770,000 migrants have arrived, most of them from Turkey.

Greece has struggled to respond, sparking anger among its European partners as unregistered migrants move further north.

The border and coast guard would monitor EU borders to the outside world — like Greece's — and have the right to send border guards, ships, planes or other assets when a country is unable or unwilling to enforce border laws.

"The agency will be empowered to require member states to take corrective measures. The decisions of the agency will be binding," warned Dimitris Avramopoulos, the EU's top migration official.

Since July, Greece, Italy and Croatia have proven unable to register even half of the people fleeing conflict or poverty who have entered their territories and then moved on toward countries like Germany and Sweden.