The deal will be signed on Monday and announced officially on Tuesday, Dow Jones reported, quoting anonymous sources familiar with the negotiations.

Deutsche Telekom and France Telecom will have equal participation in the joint venture, which will have about 30 million customers and will unseat Telefonica's O2 as the U.K.'s largest mobile operator, according to Dow Jones.

The deal will likely attract the attention of U.K. and E.U. regulators, the wire service reported.

France Telecom didn't immediately respond to a request for comment from IDG News Service on Monday. A Deutsche Telekom spokeswoman said via e-mail that the company doesn't comment on "rumours and speculations."