The boards of NYSE Euronext and Deutsche Boerse AG are expected to meet on Tuesday to give final approval to a deal, the details of which are still being thrashed out, a source close to the deal said.

Most of the tough decisions, including the composition of a combined company's board, have been made, but a deal is not done yet, the source said. The companies are working toward an announcement on Tuesday, the source added.

Important points such as the exact exchange ratio and premium for the deal are yet to be decided, the source said.

All the existing brand names will stay in place in a combined company, the source said.

The only question is around the name of a new Dutch holding company being contemplated in a merger, and that has not been decided yet, the source said, declining to be named because talks are not public.

The two powerhouse exchange operators said on Wednesday they were in advanced talks to merge, just hours after London Stock Exchange unveiled a bid for Canadian market operator TMX Group.-Reuters