PARIS, March 19 (Reuters) - Airbus has called off talks to buy the BDS cybersecurity unit of France's Atos , sending shares of the French software company tumbling 18% in early trading.

It is the second time in a year that the European planemaker has axed proposals to buy assets of debt-laden Atos after it declined to make an offer for a minority stake in a broader business a year ago following a backlash from its own investors.

Atos, which in January named its fourth new chief executive in less than two years, and saw talks over another potential sale collapse last month, has grappled with a series of profit warnings and is looking to raise funds to deal with its debt.

"Atos is analysing the resulting situation and actively evaluating strategic alternatives that will take into consideration the sovereign imperatives of the French state," it said in a statement.

Airbus said it had taken the latest decision "after careful consideration of all aspects of a potential acquisition" of the big data and security activities.

Atos' shares fell around 18%. Airbus rose around 1%.

"The failure of this sale process poses both a liquidity problem...and a problem regarding debt restructuring," analyst Nicolas David from Oddo BHF said.

Home to assets deemed strategic by the French government, Atos' woes have drawn the attention of French lawmakers and are the subject of hearings in the Senate.

Atos, a former member of France's CAC 40 blue-chip index, has seen its share price plummet over the last two years after a string of setbacks that included a badly received takeover plan for U.S. rival DXC in 2021.

The latest setback comes weeks after talks between Atos and Czech billionaire Daniel Kretinsky over the sale of Atos' legacy operations also collapsed, though some media have reported that he is considering a fresh bid.

A person familiar with the matter said Airbus had pulled out of the BDS talks due to concerns over risk and the broader turmoil surrounding Atos.

Airbus declined to add to its brief statement over ending the BDS takeover talks.

There was no immediate comment from the finance ministry or from Atos' leading shareholder, One point.

The European aerospace giant has been seen as concerned that its position in an increasingly software-focused defence industry would be at risk if the Atos activities were absorbed by a rival such as French defence firm Thales.

Thales CEO Patrice Caine recently played down suggestions that Thales could buy all or part of BDS, which Airbus had tentatively offered to buy for 1.5 billion to 1.8 billion euros, but didn't rule out any specific transaction. (Reporting by Olivier Sorgho and Diana Mandiá in Gdansk, Tim Hepher and Ingrid Melander in Paris; Editing by Bernadette Baum)