(CNN) The European Union has failed to set a firm deadline to end its contribution to climate change, after a group of central and eastern European countries blocked a proposal to slash EU carbon emissions to net zero by 2050.

Leaders of the bloc's 28 member states agreed instead on Thursday to start working on " a transition to a climate-neutral EU.

A majority of EU nations were hoping for a much more robust version of the plan. Earlier proposals envisioned a strict road map of how to reach net zero emissions, and a hard 2050 deadline. Such deal would have been notable for its sheer scale -- more than 500 million people living in the EU would have been affected by it.

However, the agreement's language was significantly watered down in the days leading up to today's summit, creating ambiguity around the deadline. While many nations supported a firm deadline for cutting emissions, a few outlying countries have been wary of its potential impact on jobs and industries.

By the end of the meeting, even the weaker version proved too strict for a group of nations led by Poland. Veto votes from Poland, the Czech Republic, Hungary and Estonia meant the proposed 2050 emissions target became a mere footnote, which specified that a "large majority of member states" should achieve climate neutrality by 2050.

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