"We remain eminently sceptical on the option of military intervention... anticipated in this resolution. We see in it considerable risks and dangers. That is why we could not approve this part of the text," a statement said.
“The dictator must immediately stop all violence against his people. He must leave power and suffer the consequences of his crimes," Westerwelle said.
Responding to accusations that Germany was isolated within the European Union and the NATO alliance with its actions, Westerwelle said the decision to deploy troops was one the country alone could take.
Germany's international partners respect and understand Berlin's decision to abstain from a United Nations resolution on a no-fly zone over Libya, he said.
"I can assure you that we had respect and understanding for our position and our decision even from those that voted in favour" of the resolution to establish the no-fly zone, Westerwelle said.
He added: "I have great understanding for the motives of those that voted for the resolution and the military action."
The UN Security Council voted Thursday to permit "all necessary measures" to impose a no-fly zone, protect civilian areas and impose a ceasefire on Qaddafi's military.
Enforcement will rely on air power as the resolution rules out sending ground troops.
The UN vote passed 10-0 with five abstentions in the 15-member council. Permanent members China and Russia were among those abstaining, but did not use their veto power. India and Brazil also abstained.
Diplomats indicated that air strikes from a coalition led by Britain, France, the US and some Arab countries could now be imminent. Canadian media said Ottawa would also send warplanes.
The European Union on Friday welcomed the resolution as the head of the European Parliament said "there was no time to waste" to enforce it.
In a joint statement, EU president Herman Van Rompuy and EU foreign affairs chief Catherine Ashton said they fully endorsed "the UN demand for a complete end to the violence and all attacks against, and abuses of, civilians."
Reiterating the 27-nation bloc's call for Qaddafi to relinquish power immediately, they urged Libya to rapidly embark on an orderly transition to democracy through broad-based dialogue.
Resolution 1973 "provides a clear legal basis for the members of the international community to provide protection to the civilian population," the statement said.
"The European Union is ready to implement this Resolution within is mandate and competences," they said.
Libya, despite condemning the resolution as a threat to its unity, said it was ready for a ceasefire with the rebels but wanted to discuss the terms of its implementation, Deputy Foreign Minister Khaled Kaaim told reporters.
Kaaim indicated Libya would "react positively to the UN resolution, and we will prove this willingness while guaranteeing protection to civilians."