The state-owned carrier notified American Airlines last month that it was interested in buying up to 10 percent of its shares but would not exceed 4.75 percent without the approval of American's board.

"We will be able to start buying shares in the open market soon, depending of course on what is the share value," al Baker told reporters in Dublin, where he was launching a new Qatar Airways route.

The share purchases will start as soon as Qatar receives regulatory approval, he said.

However, American said in a regulatory filing dated June 22 that company rules prohibit anyone "from acquiring 4.75 percent or more" of the company's shares in issue without prior board approval.

Shares in American were up 0.5 percent at $51.53 at 1342 GMT on Thursday, valuing the company at over $25 billion.

The move by Qatar Airways would expand its investments to North America at a time when Qatar is embroiled in the region's worst diplomatic crisis in years and is locked in an airspace rights row with three other Gulf states.

Qatar has no intention of going above 10 percent, al Baker said.

Al-Baker said American's CEO Doug Parker told him at an airline conference in Mexico last month that he was against Qatar's planned investment and that he would not recommend that the board approve the purchase of a stake of over 4.75 percent.

"He categorically told us that he was not interested, that he would not suggest to his board to allow us. However, I told him we can still take 4.75 percent and we will do that," al Baker said.

"Maybe once we have taken that 4.75 and they see the value that Qatar Airways brings to the table for them that they will reconsider," he said.

ANTI-GULF STANCE

He said he had no ambition to influence American's management or soften what he said was its "anti-Gulf stance."

Along with United Continental Holdings Inc (UAL.N) and Delta Air Lines (DAL.N), American has pressed the U.S. government to curb U.S. flights by Qatar Airways and rival Gulf carriers Emirates [EMIRA.UL] and Etihad Airways.

The U.S. carriers charge that their Gulf rivals have received billions of dollars in unfair state subsidies, allegations the Gulf carriers deny.

A stake in American Airlines would add to Qatar Airways' investment portfolio. The Middle East's second biggest airline also has a 20 percent stake in International Airlines Group (ICAG.L), the owner of British Airways, Iberia, Aer Lingus and Vueling, and a 10 percent stake in Chile's LATAM Airlines LAN.SN.

Qatar Airways, American Airlines, British Airways, Iberia and LATAM are all members of the oneworld airline alliance.

British Airways and Qatar Airways have a revenue-sharing partnership between their respective hubs in Doha and London, and Qatar Airways plans to launch flights to LATAM's base in Santiago, Chile.

Al-Baker made repeated digs at American, saying it wanted to keep out the Gulf carriers from the U.S. market so it could "swindle their customers."

"My dear friend Doug Parker, a big supporter of oneworld ... is now frightened of a oneworld carrier wanting to take a stake," he said.