RAMALLAH, Feb. 1 (Xinhua) -- Secretary General of the Palestine Liberation Organization (PLO) Saeb Erekat slammed Thursday the U.S. decision to add Islamic Hamas movement leader Ismail Haniyeh to "terrorist list."

"PLO rejects and condemns the U.S. finance department's decision to add Islamic Hamas movement chief Ismail Haniyeh to the terrorist list," Erekat said in a press statement.

He urged for the end of internal division and the achievement of national unity in order to protect the national project to fight back the "schemes that aim at liquidating this national project."

The U.S. State Department on Wednesday added Hamas leader Ismail Haniyeh into its terrorist list.

Haniyeh, leader and chief of the Political Bureau of Hamas, was designated as Specially Designated Global Terrorists (SDGTs) together with three other groups.

All of their properties and interests in property subject to U.S. jurisdiction will be blocked, and U.S. citizens are generally prohibited from engaging in any transactions with them. They will also be denied access to the U.S. financial system.

Hamas slammed on Wednesday the U.S. decision to list the Hamas chief into the terrorist list. The movement's leaders said they considered the U.S. decision as "ridiculous."

"This will never break our determination to carry on with resistance and stick to it until getting rid of the Israeli occupation," said Hamas spokesman in Gaza Hazem Qassem.

Hamas was designated in 1997 as a Foreign Terrorist Organization and in 2001 as an SDGT by the United States.

U.S. State Department said Haniyeh "has reportedly been involved in terrorist attacks against Israeli citizens."

It added that Hamas has been responsible for the death of 17 U.S. citizens killed in terrorist attacks.