LONDON (Reuters) - Legislation may be needed to mandate halving the time it takes to settle a stock trade in the European Union to catch up with Wall Street, given the "doubling down in opposition" from market participants worried about costs, EU officials said on Tuesday.

The 27-country bloc has said it is a matter of how and when, rather than if, the EU will cut the time it takes to complete a stock trade on Deutsche Boerse, Euronext and other platforms to one business day, or T+1, from two at present.

The U.S. moved to T+1 last month, along with Canada and Mexico to cut risk in markets, with Britain also planning to follow suit by the end of 2027 at the latest.

"Nothing in EU law stops the market from moving to T+1 tomorrow, if that is what it wants," Jennifer Robertson, a head of unit at the European Commission told a QED event.

"Legislation might be necessary, which is what stakeholders are favouring," Robertson said, adding there is also a strong call from industry for the EU to coordinate its move with Britain and Switzerland, given how capital markets are interlinked.

A decision on legislation will be taken by the new European Commission, which takes up post in the autumn, Robertson said.

The switch on Wall Street was led by the Securities and Exchange Commission, which has suggested that Europe fixes a date and sticks with it to avoid drift.

EU securities watchdog ESMA is due to set out a possible roadmap to T+1 by early 2025, and Carsten Ostermann, ESMA's head of markets, said he hoped it would be by the end of this year.

"It seems like we are going to need Level 1 change," Ostermann said, referring to existing EU law, adding it would make sense to have a steering committee to drive through the change.

"Some market participants are doubling down on opposition. We don't have everyone pulling in the same direction as we have in the US," Osterman said, adding that a shift would take a number of years.

(Reporting by Huw Jones; Editing by Peter Graff)

By Huw Jones