Doubts have emerged over talks between IAG-owned Iberia and pilots over restructuring plans involving the loss of 4,500 jobs.

Spanish pilot union Sepla agreed to negotiations over its plans to axe jobs and cut Iberia’s fleet by almost a quarter.

But the union is said to be “frustrated” after hearing no response from Iberia following preliminary talks a week ago when Sepla presented an alternative restructuring plan, and warned “time was running out”.

The pilots agreed to a pay cut of 26% and to reduce its workforce by 10%, in what it called “the most important concessions to date” but admitted that they were not optimistic about a deal being struck.

“We haven’t ruled out further strike action,” a Sepla spokesman told The Sunday Telegraph, adding that they were preparing to meet Iberia management today in a last-ditch attempt at an agreement.

A source at the carrier reportedly said that the union has taken more than two months to present a package after the restructuring was announced on November 9. The deadline to reach an agreement is the end of the month.

An Iberia spokesman said that it was still negotiating with Sepla and other unions that will be affected by the overhaul.

Iberia’s aim is “to reach an agreement” with unions, the spokesman added, but sources warned that the two sides are still “far away” from striking a deal, the newspaper reported.