BRUSSELS — The European Union’s top executive proposed a plan on Wednesday to distribute 160,000 migrants throughout the member nations, even while acknowledging that this measure alone was inadequate to the depth of the crisis.

Citing history, morality and economics, the official, Jean-Claude Juncker, the president of the European Commission, urged the bloc to put aside deep divisions over welcoming refugees from war-torn and poverty-stricken nations in the Middle East and Africa, and forge a stronger and more unified response.

Facing strong resistance by some members to a quota system that would compel them to take in a specified number of the new arrivals, Mr. Juncker cast the crisis as the most compelling one facing the bloc since World War II. He argued that it was not only a humanitarian issue, but also a test of the European Union’s fundamental ability to act in a unified manner and in accordance with its values, rather than following bureaucratic language or practices.