UNITED NATIONS (AP) – Secretary-General Kofi Annan urged Syria to cooperate fully with the U.N. investigation into the death of former Lebanese leader Rafik Hariri.

Annan made the comment Thursday when asked about the apparent refusal of Syrian President Bashar Assad to agree to be interviewed by U.N. investigators about the Feb. 14 bombing in Beirut that killed Hariri and 20 others.

A resolution approved by the U.N. Security Council “requires cooperation by all parties, including Syria, and Syria has indicated that they will cooperate, and I urge them to cooperate and cooperate fully.”

On Wednesday, Annan appointed Serge Brammertz, a Belgian who is deputy prosecutor at the International Criminal Court, to lead the next stage of the investigation. He will replace German prosecutor Detlev Mehlis who decided to step down after the probe was extended beyond six months.

In his final report to the U.N. Security Council in December, Mehlis said new evidence strengthened his initial belief that the Syrian and Lebanese intelligence services had a hand in Hariri’s assassination He said there were 19 suspects so far, including six high-ranking Syrian officials, and detailed how Damascus had tried to hinder the probe.

Annan said interviewing Assad will be one of the issues Brammertz will have to deal with after he arrives in Beirut next week.

“I’m sure Brammertz will make an early contact with the Syrian authorities and with the Syrians to try and move the process forward,” he said.