Britain supports setting up an EU military centre and is "confident" that plans will be settled on Thursday, a defence ministry spokeswoman told AFP, following earlier British objections to the project.

"We support the MPCC," the spokeswoman said on Wednesday in reference to a Military Planning Conduct and Capability facility for the bloc.

"We are all confident it will get finalised tomorrow at a meeting of EU defence ministers in Brussels," she said.

The ministry's comments come after the bloc's foreign affairs chief Federica Mogherini said on Monday she believed the ministers would unanimously back the proposals.

She told reporters in Brussels she had spoken to British defence secretary Michael Fallon on Sunday, telling him that what was important after the March deal was that "once we take at 28 a political decision, then the same 28 should put the same energy into making it operational."

"I would not understand any minister putting an obstacle between a political decision and implementation," she added.

The new facility would initially coordinate three "non-executive military missions" training government forces in Mali, the Central African Republic and Somalia.

Spanish Foreign Minister Alfonso Dastis previously said the 27 other member states wanted to approve the text Monday but could not because of British opposition.

He expressed concern that the same could happen at Thursday's defence ministers' meeting, but his British counterpart Boris Johnson said Monday the differences had been overdone.

"We understand the vital importance of European countries working together to strengthen our defences," he said.

"If they want to come together... with other arrangements, then we don't want to stand in their way. We just (need to) work on the language to make sure that we get it totally right," Johnson said.

EU diplomatic sources said the British government was cautious of not being caught out ahead of the country's June 8 general election, whose dominant theme is Brexit.