"The time for ruses and little tactical games is over," said German foreign minister Guido Westerwelle in a statement on Saturday, calling for the monitoring mission to begin as soon as possible.
He directly addressed Syrian President Bashar al-Assad, whose forces have been conducting violent operations against Syrian rebels and citizens for the past 13 months, killing thousands of people.
"More than ever it is time for the regime of Assad to end the violence unconditionally across the country so the ceasefire can be entirely respected," said Westerwelle.
The foreign minister made the statement in reaction to a unanimous vote by the UN Security Council on Saturday to pass a resolution allowing a 300-strong ceasefire monitoring mission in Syria - despite strong doubts from many Western nations.
The UN move comes just over a week after German Chancellor Merkel and US President Obama agreed that "more resolute" action by the Security Council was needed in Syria, according to a statement by the White House on April 12.
"With this mission... the international community now has a means of controlling the situation in Syria," said German foreign minister Westerwelle.
Under UN resolution 2043, the unarmed military observers will be sent for an initial period of 90 days if UN leader Ban Ki-moon decides it is safe for them to go.
In a separate statement French foreign minister Alain Juppe said the results of the mission would determine the UN's next move.
"If we are forced to note once more that the Syrian regime has not respected its obligations, the Security Council will have to examine, as quickly as possible, every option," he said.
The council has already approved an advanced mission, but several western envoys stressed the dangers of sending unarmed monitors to Syria where violence has not halted since an official cessation of hostilities began on April 12.