The European Parliament and EU member states agreed on Wednesday a target to cut carbon emissions by at least 55 percent by 2030, in what was called a "game changer" just ahead of a US-hosted climate summit.
The deal, reached before dawn after 14 hours of negotiations, sets about putting parts of the 2016 Paris climate accord into binding legislative effect across a range of sectors, underpinning the European Union's ambition to lead the world on the issue.
The EU vice president responsible for the bloc's Green Deal, Franz Timmermans, called the agreement "a landmark moment for the EU and a strong signal to the world" alongside a 5:00 am tweeted picture showing the moment it was struck.
But top environmental groups Greenpeace and WWF immediately slammed the agreement as insufficient to limit global warming to the 1.5-degree-Celsius threshold enshrined in the Paris accord.
Greenpeace noted that Britain, a former EU member, vowed this week to slash carbon emissions by 78 percent by 2035.
The EU climate law agreement ended a deadlock between member states, which insisted on the 55-percent goal agreed in November, and MEPs who wanted the target hiked to 60 percent.
The EU announcement and the wider debate will feed into a virtual climate summit hosted Thursday and Friday by US President Joe Biden, who has made climate a top priority. He is expected to unveil ambitious new US targets on reducing carbon emissions.
Biden has invited 40 world leaders to the online gathering. Chinese President Xi Jinping -- leader of the biggest carbon-emitting country -- has said he will attend.
The EU views itself as the prime mover in getting the world to reduce greenhouse gases, leveraging its global standard-setting weight on climate as it has already done in terms of data protection and trade.
European Commission chief Ursula von der Leyen tweeted that "our political commitment to becoming the first climate neutral continent by 2050 is now also a legal one".
Last month she predicted the proposed EU climate law would "inspire many of our partners to raise their own ambition".
- Sweeping ambition -
However the EU executive faces challenges as it looks to reform its legislation on everything from transport to taxes to energy so they all reflect the shift to a green-friendly future.
Among those are plans to levy a carbon border adjustment mechanism -- a tariff on goods imported into the EU by countries that are not as ambitious in their carbon-emission goals -- and division among EU member states as to whether plants powered by nuclear energy or natural gas can be considered "green".
The chair of the European Parliament's environmental commission, Pascal Canfin, told journalists that the 55-percent target had to be accepted but the way net carbon emissions are calculated was changed "to be able to move de facto, in reality, from 55 to close to 57".
He said 52.8 percent of the carbon emission cuts would be "direct reductions" with the rest made up by calculations on carbon sinks, which are made up of plants, the soil and the sea.
"This climate deal is a game changer," he said.
In the EU and Britain, the baseline year emission-reduction targets are weighed against is 1990, while for the United States and China it is 2005, resulting in different calculations on headline goals.