Senior Palestinian official Mr Saeb Erakat called today for the "immediate" release of Palestinian radical chief Abu Abbas.
Mr Erakat said the arrest of Abbas by US forces in Baghdad violated a 1995 peace accord.
"We ask the US administration for the immediate release of Abu Abbas and for it to respect the 1995 interim agreement between the Palestine Liberation Organization and Israel . . . and signed by [then] US president Bill Clinton," he said.
He pointed to one of its clauses that says PLO members cannot be arrested or tried for acts committed before September 1993.
He said Abbas, who has lived most his life in exile, had "visited the West Bank and Gaza Strip several times with Israel's co-ordination and for this reason we call on the US administration to respect this agreement and liberate Abu Abbas straight away."
But the interim peace accord, signed in Washington in 1995, is a bilateral accord that does not set out any US commitment to immunity for acts against US citizens.
Abbas, who masterminded the hijacking of the Achille Laurocruise ship in 1985, was captured in Baghdad by special operations forces backed by US army troops.