Negotiations have resumed between a grocery workers union and three US supermarket retailers, aimed at ending a four-month-long labour dispute in Southern California.

The talks, supervised by Federal Mediation and Conciliation Service director Peter J Hurtgen, are the first mediated talks between US grocers Albertsons, Kroger and Safeway, and the United Food and Commercial Workers union since December, when the last round of negotiations broke down.

Hurtgen said he had re-started the talks because he saw the potential for progress on the key issues, reported Reuters.

Around 70,000 workers are involved in the dispute, which centres on health care contributions.