* Commission proposes 2030 emissions targets for EU 28
* Brexit could force revision of law, diplomats say
* Targets disputed by likes of Poland, Ireland (Adds Polish reaction)
By Alissa de Carbonnel
BRUSSELS, July 20 (Reuters) - EU regulators handed out bitterly disputed national emissions-reduction targets on Wednesday for spreading the burden of the bloc's climate goals by 2030, despite risks Britain's exit could unravel the effort to fight global warming.
As the first major piece of legislation since Britons voted in June to leave, it is a test of the union's cohesion, as it seeks to keep to a pact agreed in Paris last year aimed at holding global warming "well below" 2 degrees Celsius.
It assigns EU nations targets for slashing greenhouse gas emissions ranging from zero to 40 percent to achieve the bloc's overall goal of at least 40 percent below 1990 levels by 2030.
The European Commission has spent months in shuttle diplomacy with national governments to work out the politically sensitive targets, which will require an economic shift to low-carbon technology in big employment sectors such as transport, farming and building.
"All member states understand very well that if you want to alleviate the burden on one country, than someone else will have to carry it," European Commission Vice-President Maros Sefcovic told Reuters. "I'm sure that the discussion will be intense."
Poland, whose economy relies heavily on coal, objected to its target, just hours after it was announced by Brussels.
"Poland cannot afford such a big reduction effort," Pawel Salek, Poland's deputy environment minister in charge of climate policy, said in an email.
The proposal needs the support of EU governments and of the European Parliament - a lengthy proicess of up to two years.
For now, the draft law sees Britain, the bloc's second-largest emitter after Germany, cutting pollution by 37 percent by 2030 from 2005 levels, more than most other EU nations. But Brexit could upend the law, diplomats say.
"We cannot do nothing. If something happens, we will adapt," Climate and Energy Commissioner Miguel Arias Canete said. "We have to have a signal to industry and to stakeholders."
Under the proposal, which covers sectors outside the EU's Emissions Trading System (ETS), Germany's target is a cut of 38 percent and France's is 37 percent. Poland needs to reduce discharges by 7 percent.
The strictest target of 40 percent cuts has been assigned to Luxembourg and Sweden. Finland and Denmark are projected to reduce emissions by 39 percent. These states will be allowed to use a limited amount of carbon permits to be auctioned as part of the ETS to meet their target.
Bulgaria is the only EU nation asked to keep discharges unchanged.
In a policy innovation, countries with high emissions from agriculture may offset these against a limited amount of credits from well-managed farmland or forests, which absorb carbon dioxide - a provision criticised as a loophole by green groups.
AMBITION WITHOUT BRITAIN?
Without Britain, the remaining 27 nations could either weaken climate goals, triggering international criticism, or step up ambitions already contested by states that rely on polluting sectors such as coal in Poland or farming in Ireland.
"It's one rich country less to take on some of the burden from the Poles," one EU diplomat said.
Environmental campaigners warn the effort is too shallow to prevent the worst effects of climate change, blamed for calamitous weather. The Paris agreement set an aspirational goal of 1.5 degrees Celsius.
When EU environment ministers wrestle over the proposal later this year, Britain will still have a seat at the table. It remains bound by the bloc until its formal withdrawal - a two-year process yet to be launched by new Prime Minister Theresa May.
The Commission also proposed on Wednesday limits for the first time on CO2 emissions from trucks and buses as well as new fuel-efficiency standards for cars and vans from 2020. (Additional reporting by Agnieszka Barteczko in Warsaw; Editing by Dale Hudson and Adrian Croft)