European Union plans to require the aviation sector to use more sustainable fuels are not ambitious enough and the EU should let member states set their own tougher requirements, seven countries have said.

The European Commission last summer proposed measures to tackle greenhouse gas emissions from aviation, as part of the EU's goal to cut overall net emissions 55% by 2030, from 1990 levels.

The EU plan would force suppliers to blend at least 2% of sustainable aviation fuel (SAF) into their kerosene from 2025, rising to 5% in 2030 and 63% in 2050.

In a letter sent to the Commission's climate and transport policy chiefs on Monday, seven countries said that while the EU-level requirements were needed, the proposal should also allow countries to go further.

"We believe there is room for increasing the ambition further regarding sustainability and boosting of SAF by allowing member states to go beyond minimum EU standards," said the letter, reviewed by Reuters.

Higher national targets would not distort competition in the EU market, the letter said. It was signed by ministers from Austria, Denmark, Finland, Germany, Luxembourg, the Netherlands and Sweden.

Danish climate minister Dan Jorgensen said the climate change emergency "demands bolder action" than the EU proposal, which fell short of Denmark's pledge to make domestic flights fossil fuel free by 2030 - a target also set by Sweden.

"Unfortunately, the current proposal from the Commission will put a brake on our aspirations to spearhead the greening of aviation," Jorgensen said.

SAF, which can be produced from biomass or renewable energy, is seen as crucial to cut emissions from flights this decade, in the absence of technologies such as large electric planes.

The countries said higher national targets would incentivise more SAF production and bring down costs sooner. Factors including high costs have hampered demand so far, and SAF currently account for less than 1% of Europe's jet fuel consumption.

The EU proposal must be negotiated and approved by a majority of EU countries and the European Parliament.