United Technologies and Raytheon (RTN) - Get Report are in talks to combine in an all-stock deal, The Wall Street Journal reported, citing a person familiar with the matter.

The companies, which together have a market value of roughly $166 billion, could announce a deal in the coming days, the person told the Journal. Reuters said a deal could be announced Monday if the negotiations are completed successfully.

Exact terms of the transaction couldn't be learned but the Journal said United Technologies shareholders are likely to own a majority of the combined company. The deal would be structured as an all-stock merger of equals.

A merger of United Technologies and Raytheon would form the world's second-largest aerospace-and-defense company by sales after Boeing (BA) - Get Report .

The merger wouldn't affect United Technologies' plans to spin off its Otis elevator and Carrier businesses into separate companies. Raytheon would be combining with United's remaining aerospace business, and all transactions would take place at the same time, the Journal noted.

United Technologies CEO Greg Hayes is expected to lead the new company, while Raytheon CEO Thomas Kennedy would be chairman.