The London Stock Exchange has said its £21 billion merger with Germany's Deutsche Borse is likely to be blocked by the European Commission.
The LSE said the commission had made the "disproportionate" request that it sells its stake in MTS, an electronic market.
The stock market said that, with its shareholders' best interests in mind, it could not go ahead with the request but would continue to pursue the merger.
The LSE said on Sunday: "Based on the commission's current position, LSE believes that the commission is unlikely to provide clearance for the merger.
"Nevertheless, the LSE board remains convinced of the strategic benefits of the merger and recognises the strong support from shareholders for the transaction.
"LSE will continue to take steps to seek to implement the merger."