The United Nations will have its complete team of 300 military observers and 100 civilians in Syria by June, UN Secretary General Ban Ki-moon, DPA reported.
Attending an Atlantic Council event in Washington Monday, Ban called for more engagement by the international community to halt the violence that has continued in Syria for more than a year.
He said the Syrian government "continues to assault its people."
"We cannot predict how this will end," he said. "But we do know there can be no compromise on fundamental principles of justice and human rights, in Syria or elsewhere."
On Monday, Syria held long-delayed parliamentary elections, which were panned by foreign governments, the UN and domestic opponents of President Bashar al-Assad's regime. Damascus claimed "considerable" voter turnout, which the opposition ridiculed.
The elections, initially scheduled for September, were postponed due to the uprising since early 2011 against al-Assad, in which 9,000 people have died, according to UN estimates.
Kofi Annan, special envoy to Syria for the UN and Arab League, was due to deliver a briefing Tuesday on the observer mission.
Fifty UN observers are in Syria to monitor a ceasefire which went into effect on April 12 but has repeatedly been violated by both sides. More observers are due to arrive next week.
Annan's plan calls for access to humanitarian services and talks between the government and the opposition.