Iberia may become the subject of a bidding war, experts say.

Air France-KLM has reportedly partnered with private equity group Apax to buy Europe's fourth largest airline.

BA and private equity groups TPG Capital, Vista Capital, Inversiones Ibersuizas and Quercus Equity have offered 3.4bn euros ($4.6bn; �2.3bn).

BA already owns a 10% stake in Iberia and has an option for another 30%.

Offer hopes

Apax declined to comment on reports that it is working with Air France-KLM to table a bid.

However, observers believe a bidding war may break out for Iberia, following the latest comments from Air France-KLM.

Air France-KLM said will actively promote consolidation of the industry.

"In Europe, Spain is one of the major markets and Iberia an important player in air transport," the group said in a statement.

Iberia also has lucrative routes to South America,

"Taken in the perspective of much-needed consolidation for the efficiency and profitability of the air transport sector, it is therefore quite normal for it to be examined among others," it added.

Meanwhile, German flag carrier Lufthansa has repeated that it is interested in Iberia, but added that the cost of a takeover was probably too high.

Takeover rumours surrounding Iberia have taken off after an "open skies" deal was agreed between the US and Europe.

Analysts have long said that the deal would lead to consolidation in the industry, and that it would make Iberia an attractive target.