Stock exchange operators Deutsche Boerse and London Stock Exchange (LSE) said Tuesday they would offer to sell French clearing house LCH Clearnet as they push for regulatory approval of their planned merger.

The two firms, whose operations include the London and Frankfurt stock markets, "decided to formally submit the divestment of LCH Clearnet SA by LCH Clearnet Group as a remedy to the European Commission in order to address anti-trust concerns," they said in a statement.

Plans to offload the French arm of LSE's clearing house business have been brewing since early January, when the British firm agreed to sell it to European rival Euronext.

If the merger with Deutsche Boerse -- in the works since February 2016 -- goes ahead, Euronext will buy LCH Clearnet for some 510 million euros ($545 million).

Monday evening was the deadline for Deutsche Boerse and LSE to offer remedy proposals to alleviate Brussels' competition fears over their tie-up.

It remains to be seen whether EU authorities, who opened an in-depth probe in September, will accept the sale as sufficient to assure the deal is waved through.

The proposed deal has drawn sharp rebukes from France, Belgium, Portugal and the Netherlands, fearful for their own stock exchanges, owned by Euronext.

Deep concerns over competition helped scupper two earlier attempts by the companies to merge, in 2000 and 2005.

And Britain's vote to quit the European Union in June has not helped the merger's cause, with German regulators reluctant to see the Frankfurt exchange managed from London.

The Commission now has until March 13 to make a decision, and will "consult market participants" to determine whether the sale of LCH Clearnet is enough to placate competition fears.

Deutsche Boerse's supervisory board issued a second statement Tuesday saying that it "unanimously expresses its full confidence in the chief executive Officer Carsten Kengeter".

German authorities have been investigating Kengeter since last week on suspicion of insider trading.

The allegations relate to Deutsche Boerse shares Kengeter bought in December 2015, two months before the merger plans became public.