MADRID - Spanish banks are poised to sign up to the mortgage-relief measures that the government proposed on Tuesday to support vulnerable and middle-class families as living costs soar, the head of Spain's main banking association said on Wednesday.

The package, aiming at helping more than one million vulnerable households and middle-class families cope with higher interest rates and living expenses, is a set of voluntary measures that would become mandatory once the banks agree.

"The lenders will still have to take the time to review the texts in detail and, in some cases, to pass through their governing bodies," AEB's head Alejandra Kindelan told reporters on the sidelines of a financial event.

Most of the country's largest banks such as Santander , BBVA, Sabadell and Bankinter are members of AEB.

Santander, Spain's biggest lender, warned on Tuesday that the measures could lead to higher bank provisions and more barriers to credit for customers, while other major banks said they were still studying the fine print.

The planned measures, such as extending loan repayments, are part of a wider package of support to help ease cost of living pressures, including a rebate on fuel costs and windfall taxes. Other countries, such as Hungary, Portugal, Poland and Greece, have approved different forms of mortgage support.

Economy Minister Nadia Calvino gave banks a month to sign up ahead of its planned implementation next year.

(Reporting by Emma Pinedo, editing by Inti Landauro and Bernadette Baum)