The Defense Security Cooperation Agency said it had approved the sale for $6.9 billion of four Lockheed Martin combat frigates, known as multi-mission surface combatant ships, just 10 weeks after Athens signed a memorandum of understanding with Paris on a similar deal for French-built ships.

The agency also approved a $2.5 billion Lockheed program to upgrade Greece's MEKO class frigate, including adding and upgrading weapons systems and electronics.

The announcement suggested that France faces a fresh commercial arms deal threat after the United States wrested away a massive submarine contract for Australia in a shock announcement on September 15 that ruptured relations between Washington and Paris.

France recalled its ambassadors to the United States and Australia and labelled it a "stab in the back" by an ally when Canberra ditched a longstanding deal worth billions of euros to buy conventional French submarines for US nuclear-powered vessels.

Two weeks after that, Greek Prime Minister Kyriakos Mitsotakis set a memorandum of understanding with President Emmanuel Macron for France to buy three and possibly four French Belharra frigates for three billion euros ($3.5 billion).

The French ships would be built by Naval Group for delivery beginning in 2024.

In the France-Greece deal, the two sides had until the end of this year to reach a final agreement.