European Commission President Jean-Claude Juncker is due to announce plans to tackle the migrant wave which has thrown European policy into disarray.
Under the proposals, 120,000 additional asylum seekers will be distributed among EU nations, with binding quotas, BBC reported.
Germany, the main destination for many migrants, supports quotas, but some EU countries oppose a compulsory system.
Juncker's plans expand upon quotas for the relocation of 40,000 migrants in Italy and Greece proposed in May -- though governments only actually agreed to take 32,000.
The fresh plans for an extra 120,000 migrants would allocate 60 percent of those now in Italy, Greece and Hungary to Germany, France and Spain, reports say.
The numbers distributed to each country would depend on GDP, population, unemployment rate and asylum applications already processed.
Germany has welcomed Syrian migrants and said it expects 800,000 asylum seekers this year alone -- though not all will qualify as refugees and some will be sent back.
German Chancellor Angela Merkel said on Tuesday that quotas were an "important first step".
Speaking alongside visiting Swedish Prime Minister Stefan Lofven, she said the EU needed an open-ended "system to share out those with a right to asylum".
UN High Commissioner for Refugees Antonio Guterres has, meanwhile, labelled the EU's approach to asylum seekers "dysfunctional".
The UNHCR highlighted the growing scale of the challenge, releasing new figures that suggest it expects 400,000 migrants to have arrived in Europe by sea in 2015.
The majority are Syrian, and the UN says many are now seeking a better life in Europe because of poor conditions in refugee camps in Jordan and Lebanon -- caused in part because of a drastic shortfall in multilateral aid programmes.
