The agreement -- an amendment to a prior deal signed in 2019 -- was approved by a majority of 181 MPs, including the ruling conservative party and the socialists, state agency ANA said.

Mitsotakis had earlier told parliament the mutual defence cooperation agreement "upgrades" Greece into "the main partner and interlocutor of the United States in the broader area".

It also includes mutual protection pledges against armed attack, he said.

The deal gives US forces access to a "road into the Balkans" through additional Greek military facilities in Litochoro and Volos, the sprawling naval base of Souda and the key port of Alexandroupolis, the PM said.

The agreement amendment originally signed in Washington in October "enables US forces in Greece to train and operate from additional locations", Secretary of State Antony Blinken said at the time.

"This update will allow the agreement to remain in force indefinitely," Blinken said.

Greek officials have said the agreement will be updated every five years.

Under the 2019 agreement, US forces had already been granted priority status for "unimpeded access and use" within 48 hours at Alexandroupolis, a Balkans and Black Sea gateway of strategic value to the US navy and NATO.

Greece also seeks to turn Alexandroupolis into an energy hub through the construction of a floating liquid natural gas terminal.

Leftist former prime minister Alexis Tsipras on Thursday said the agreement "turns our country into a (US) satellite...not an ally".

Mitsotakis dismissed this as "nonsense".

Facing constant challenges in the Aegean from regional rival and NATO ally Turkey, Greece has also signed a mutual assistance defence pact and warplane and frigate deals with France.

The premier will visit US President Joe Biden at the White House on May 16 and address Congress the following day.