"The message must go out that impunity will not be allowed, and I think for most of the (UN Security) Council members, that is the objective and that will be enough," he said in Cairo on Tuesday.
He was speaking after talks with Egyptian Foreign Minister Ahmed Abul Gheit, on the second day of a visit during which he is to meet President Hosni Mubarak and Prime Minister Ahmed Nazif.
"I would expect and urge Syria to continue its cooperation with the investigation," Annan said, referring to the UN probe into the 14 February assassination of former Lebanese prime minister al-Hariri.
If the perpetrators were "made accountable, I think this will be the end", he said.
"Recently Syria has had a good record in implementation of UN resolutions. They did cooperate on resolution 1559" on the withdrawal of Syrian troops from Lebanon in April, Annan added.
"What is important is that Syria cooperates, and they must get the message loud and clear. All the 15 members of the Security Council want Syria to cooperate in the investigation."
When asked if an "Iraqi scenario" in which foreign powers resort to military options against Syria if it does not comply with the international investigation, Annan tried to allay regional fears.
UN investigator Mehlis (L) wants
to question senior Syrian figures
"I hope nobody is thinking of going in that direction. No one in the Security Council is thinking in those terms, and as I have indicated, the objective is to get to the truth and punish the perpetrators," he said.
"I think we have enough problems in the region not to open other fronts," he said.
Egypt has acted as a mediator between Western powers and the government of Syrian President Bashar al-Assad, urging the international community to show restraint and avoid measures that could provoke a regional flare-up.
Annan dismissed suggestions that a Syrian inquiry commission, which was formed by presidential decree after the release of the UN report and began its work on Thursday, would be an obstacle to the international investigation.
"Recently Syria has had a good record in implementation of UN resolutions. They did cooperate on resolution 1559"
UN Secretary-General Kofi Annan
"It could help the work of Mehlis. Mehlis himself suggested when he appeared before the Security Council that it could be a good idea for the Syrians to set up their own investigation," he said.
Abul Gheit said that Annan favoured holding a trial in Lebanon, rather than in an international court, of those involved in the al-Hariri assassination.
"Mr Annan said that the investigation could pave the way for a trial on Lebanese territory, but options remain open for an international trial," Abul Gheit said.