"Teasers have been sent," one of the sources said, referring to a document presenting the company to potential buyers.

Dialog, whose book value is estimated at more than 800 million zlotys ($281.5 million), has struggled to compete with Poland's dominant phone operator, TPSA, a unit of France Telecom.

Poland's No. 2 telecoms group, Netia has said it was interested in snapping up smaller Dialog to strenghten its position, especially in the Internet arena.

KGHM has said it wants to sell Dialog by the end of June.

The state-controlled miner is also among the owners seeking to sell Poland's No. 2 mobile operator Polkomtel, which could fetch as much as $6.2 billion.