British Airways will join forces with the US private equity firm Texas Pacific Group (TPG) in a bid for Spain's leading airline Iberia, the carrier announced Tuesday in London.

"British Airways has joined with TPG Capital, Vista Capital de Expansion, Inversiones Ibersuizas and Quercus Equity to investigate a possible consortium offer for Iberia," the airline said in an announcement to the London Stock Exchange. "There is no guarantee that a formal bid will be made."

Europe's third-largest airline said in a statement in London today that it would make no additional investment in the Spanish carrier beyond the 10 percent stake it already holds as Iberia's biggest shareholder.

Spanish investors were to control at least 51 per cent of the formerly state-owned airline, which has traditionally been strong in Latin America.

Spanish reports said the bidding consortium would also include the Spanish funds Vista Capital, Inversiones Ibersuizas and Quercus Equity. TPG had already announced a possible offer worth about 3.6 billion euros (4.8 billion dollars).

Both British Airways and Iberia declined to comment. Iberia said it expects to make further announcements Thursday after its board meeting.

Shares of Iberia rose as much as 6 cents, or 1.5 percent, to 3.93 euros and were up 0.3 percent in Madrid. Iberia stock has increased by some 42 percent this year, valuing the company at 3.74 billion euros. British Airways shares fell 1.5 percent to 473 pence.