PARIS – France launched May 2 an upgrade of systems and weapons on three La Fayette frigates, notably adding an anti-submarine capability to the stealthy warship, the arms procurement office said.

The Direction Générale de l'Armement (DGA) announced the award to DCNS for the modernization of three of the five La Fayette class frigates in service with the French Navy. Work will start in 2020 and will be done in Toulon, southern France, when the frigates go into dock for scheduled overhaul, the procurement office said. A first upgraded frigate will be delivered in 2021.

The anti-submarine capability will be fitted with a hull-mounted sonar and anti-torpedo countermeasures, the DGA said. A spokesman declined to comment on the value of the contract.

Adding the antisubmarine capability boosts the La Fayette to the first rank listing of warships.

The work on the ship includes a general overhaul of the hull and combat systems. The electronic and computer systems for managing the ship will be upgraded, while the combat management system will be replaced with a version adapted from that fitted on the Charles de Gaulle aircraft carrier.

Other upgrades include the tactical datalink and a replacement of the Crotale missile with two Sadral launchers, the DGA said.

Thales supplies the anti-air Crotale weapon, while a Sadral launcher fires MBDA Mistral missiles.

Nathalie Smirnov, DCNS director for services, welcomed the launch of the upgrade.

"This is a significant operation which has never before been undertaken on this type of frigate," she said in a DCNS statement.

The decision to upgrade La Fayette was taken at a ministerial investment committee meeting and follows last month's launch of work on the intermediate frigate, in a deal worth €3.8 billion ($4.2 billion). The aim is to equip the French Navy with a fleet of 15 first rank frigates until an initial intermediate frigate is delivered in 2023.