March 21 (Reuters) - Southwest Airlines said on Thursday ramp, operations, provisioning and cargo agents approved a new five-year labor contract.

The contract covers 18,000 workers, represented by the Transport Workers Union (TWU) Local 555.

In the past two years, unions representing pilots, flight attendants and maintenance workers have sought higher wages, better scheduling and other benefits against the backdrop of a tight U.S. labor market.

The agreement with Southwest constitutes a wage rate of $38 per hour at the top of the wage scale, which TWU had said last month was 6.6% above United Airlines' current industry leading rate. (Reporting by Aishwarya Jain in Bengaluru; Editing by Krishna Chandra Eluri)