French carmaker Renault, its Japanese alliance partner Nissan and Germany's Daimler are likely to announce partnership and cross-shareholding plans as early as Wednesday, sources told Reuters.

Renault and Daimler have been discussing a partnership as carmakers worldwide seek to become more competitive, sharing technology costs and gaining scale. The automobile sector, which is emerging from a drastic downturn, is also scrambling to meet tightening emissions rules.

Renault's board is due to hold an extraordinary meeting to discuss the plans on Tuesday afternoon, a Renault source told Reuters late last week.

Nissan is also expected to be involved in the agreement, and the three companies will likely cement the partnership with small cross-shareholdings.

Renault already owns 44.3 percent of Nissan, while the Japanese company has a 15 percent stake in its French partner.

Any equity exchange as part of a Renault-Nissan-Daimler partnership is expected to be on a much smaller scale, and represent a symbolic participation rather than a step toward the level of integration Nissan and Renault have achieved in the course of their 11-year alliance.

Daimler -- the maker of luxury Mercedes-Benz cars, which also owns the struggling Smart small-car brand -- wants to tap into Clio-maker Renault's small-car expertise, while Renault and Nissan could benefit from Daimler's engine know-how.

The announcement -- which may be made at a press conference with Renault and Nissan Chief Executive Carlos Ghosn -- will come the day after an extraordinary meeting of Renault's board of directors due to take place on Tuesday afternoon, the Renault source said.

The board is due to discuss the different elements of the agreement, including the size of possible stakes and the structure of the deal, he said.

Renault has decided on a communication plan for April 7 -- it will be a press conference with the CEO (Carlos Ghosn), I think, he added.

A second source told Reuters on Monday that the three companies would make a joint announcement, and that this could happen on Wednesday after the Renault board meeting.

A Renault spokeswoman declined to comment.

A Nissan spokesman also declined to comment. Daimler could not immediately be reached for comment.

Both companies have said they are discussing closer ties with each other as well as with other carmaking peers.

(Reporting by Helen Massy-Beresford and Chang-Ran Kim; Editing by Erica Billingham)