DAMASCUS, Syria - Syrian President Bashar Assad challenged today the basis of U.S. sanctions on his country and said he would not expel Palestinian militant groups as demanded by the United States.

Assad disputed the case that the Bush administration had made to impose the embargo, saying Syria does not have weapons of mass destruction and there is no evidence of foreign fighters crossing the border from Syria to Iraq.

"We have always asked the administration to give us one passport or one name or evidence of that (border infiltration) happening. So far, we have not had that happen," Assad told a group of American editors.

Assad met the editors at the presidential palace while they were on a fact-finding trip arranged by the Washington-based International Reporting Project.

President Bush imposed the sanctions Tuesday. They ban all U.S. exports to Syria except food and medicine and they forbid direct flights between Syria and the United States. The penalties came as a response to allegations that Syria was supporting terrorism and undermining U.S. efforts in neighboring Iraq. Bush signed the order under a law that Congress passed by an overwhelming vote late last year.

Syria hosts Palestinian militant groups such as Islamic Jihad and Hamas, which are regarded as terrorist organizations by Israel and the United States. Assad's government regards them as legitimate groups fighting Israel's occupation of Palestinian land. Syria is on the U.S. State Department's list of terrorist-sponsoring countries.

Assad said today "there are no leaders" of Hamas and Islamic Jihad in Syria, but only political spokesmen who came to Syria after being expelled by Israel.

Referring to Hamas members in Syria, Assad said: "If you ask them to go, where could they go? They have to go back to their land and Israel could put them in jail ... We don't expel people. They should go back home."

The United States has accused Syria of failing to stop guerrillas from crossing its border into Iraq.