BERLIN, March 9 (Reuters) - Emirates will press ahead with plans to launch flights on Sunday to Newark in the United States via Greece, despite attempts by members of the U.S. Congress to block the route, the airline's president said on Thursday.

Twenty-five members of Congress have written to U.S. President Donald Trump asking him to stop the flight over accusations Emirates and other Middle East airlines have violated the U.S. open skies agreement.

"We're not changing it. We have breached no terms of the air service agreement that allows us to do that," Emirates President Tim Clark told reporters at the ITB travel fair in Berlin.

Major U.S. carriers Delta Air Lines, American Airlines Group Inc and United Continental Holdings Inc have campaigned for more than two years to get the U.S. government to intervene in a dispute over subsidies.

The U.S. airlines say Emirates, Etihad Airways and Qatar Airways have received $50 billion in state subsidies in violation of the U.S. open skies air services agreement.

The Gulf airlines have repeatedly denied the accusations.

The latest Emirates route is contentious for some because it will stop to pick up passengers in Athens on its way to Newark from Dubai, its second so-called fifth freedom flight to the United States.

Fifth freedom flights are where an airline from one country operates between two different countries, the other Emirates flight to the United States being its route to New York which stops to pick up passengers in Milan.

Trump acknowledged at a White House meeting with U.S. aviation executives on Feb. 9 that U.S. carriers were under pressure from foreign airlines.

(Reporting by Victoria Bryan; additional reporting by Alexander Cornwell in Dubai; editing by David Clarke) ((victoria.bryan@thomsonreuters.com; +49 30 2888 5169; Reuters Messaging: victoria.bryan.thomsonreuters.com@reuters.net Twitter:@vl_bryan))