BRUSSELS — The European Union’s climate commissioner demanded Wednesday that E.U. member states reach agreement before the end of the year on a stop-gap measure to tackle the virtual collapse of the bloc’s main instrument for cutting carbon emissions.

The European Commission, the executive arm of the European Union, proposed on Monday to defer the auction of 900 million carbon allowances that would have been sold between 2013 and 2015, the first three years of the next phase of the E.U. Emissions Trading Scheme.

In a process known as backloading, they would instead be auctioned at the end of the phase, in 2019-2020, to reduce a glut of allowances caused by the economic slowdown in Europe.

“Market operators must have clarity before year-end on this,” Climate Commissioner Connie Hedegaard said Wednesday in a statement. “At the same time, the commission presents options for possible structural measures that can provide a sustainable solution to the surplus in the longer term.”