The two nations believe such a move would send "the wrong message to investors and society as a whole", Spanish Prime Minister Pedro Sanchez told a joint news conference in Madrid with his Danish counterpart Mette Frederiksen.

The European Commission drafted plans late last year to label gas and nuclear energy as green investments, a move it hopes will steer huge sums of private capital into activities that support EU climate goals.

But Austria and Luxembourg have along with Spain and Denmark opposed the EU's draft plans for a so-called "sustainable finance taxonomy".

Heavyweight Germany opposes labelling nuclear power as sustainable, but not gas.

Sanchez and Frederiksen believe decisions about the new rulebook should have a "strictly scientific basis", a "position shared by Austria and Luxembourg". the Spanish government said in a statement after the two leaders met.

EU member states are awaiting the commission's final proposal, which it has said it will publish soon, without giving a date.

Once published, a majority of the European Parliament or a super-majority of EU member states -- 20 of the 27 countries -- could block the rules.

It is unlikely that such a majority will be reached since a dozen nations including nuclear-reliant France back the new rulebook.