USS WASHINGTON (Reuters) - Argentina naval forces and a U.S. fleet including the nuclear-powered aircraft carrier USS George Washington carried out naval exercises on Thursday in waters off the South American nation, a show of closer ties under new President Javier Milei.

The joint exercise, called "Gringo-Gaucho" in a tongue-in-cheek reference to slang terms for Americans and Argentines, is the first such operation since 2010 and comes less than six months into the libertarian Milei's administration.

"This is to show our friendship, our allyship, and our partnership," said U.S. Commander Alexis Walker during the drill, which took place about 300 kilometers (186 miles) off the coast of the popular tourist city Mar del Plata.

Defense Minister Luis Petri described the opportunity to train alongside U.S. forces as "transcendental" while lauding U.S. armed forces as the most formidable worldwide.

"Relations are really, really good right now, and I'm really happy with the relationship," said U.S. Ambassador to Argentina Marc Stanley, noting that Milei's government has recently bought U.S.-made F-16 fighter jets, as it mulls other military aircraft purchases.

Milei, a right-wing economist and former pundit, has visited the United States several times since he took office last December. He has hosted a steady stream of senior U.S. officials in Argentina, pledging tighter ties while also offering more criticism of China and Russia.

(Reporting by Miguel Lo Bianco; Editing by Adam Jourdan and Leslie Adler)

By Miguel Lo Bianco