They said that the agreed locations for the bases could be "put in harm's way if the US enters into an international armed conflict even if the potential US conflict is not geographically in the Philippines."

Among the provisions of the Constitution that were violated by EDCA is the prohibition on nuclear weapons in the country. The petitioners said there was "no absolute" statement in EDCA that prohibits the entry of nuclear weapons into the country, only saying that it disallows the prepositioning of nuclear weapons.

Earlier, Bayan Muna (Country First) Representative Neri Colmenares said that EDCA would make the Philippines "the biggest US military base in the world."

"This will make the Philippines the biggest (US) military base in the world. By the stroke of a pen, through EDCA, the Aquino government ceded all Philippine sovereignty to the US and make us second class citizens in our own country. This agreement is very unequal and extremely disadvantageous to Filipino interests," Colmenares said.

Earlier, Senator Miriam Defensor Santiago said that she is confident that the Supreme Court would declare EDCA unconstitutional.

"An agreement signed by a defense secretary and a US ambassador should not be the new normal. It should be declared abnormal, because of the particular importance of EDCA in the context of our Constitution," Santiago said in a statement.

An international law expert, Santiago said that under international law, the heads of state are the ones who should sign "treaties of particular importance" and if representatives are sent to sign on their behalf, they need to show a formal document known as "full powers."

Santiago said that Defense Secretary Voltaire Gazmin and US Ambassador Philip Goldberg, who signed EDCA, did not present any document showing that they were given full powers.

She added that EDCA should have been submitted first to the Senate for ratification.

EDCA was rushed for signature by Gazmin and Goldberg a few hours before the arrival of US President Barack Obama for an overnight stay in Manila on April 28.