MADRID (Reuters) - French private equity firm PAI Partners teamed up with Spanish peer Inveready to make an offer to buy Spain's fifth largest telecom company Avatel, Expansion newspaper reported on Monday citing unidentified market sources.

The alliance is not the only bidder for Avatel, which is worth about 550 million euros ($592.41 million) but is the one closest to seal the deal, the newspaper said.

The acquisition could be signed by the end of this month, Expansion added.

Spokespeople at PAI Partners, Inveready and Avatel did not respond to requests for comment.

Avatel, the fifth largest telecom operator in Spain in terms of sales, has created a national telecom network after buying more than a 100 small regional operators.

($1 = 0.9284 euros)

(Reporting by Inti Landauro, Editing by Louise Heavens)