Norwegian army Maj. Gen. Robert Mood halted monitoring efforts Saturday after his observers came under direct attack.
"I made that decision based on the risks on the ground and based on the fact that risks made it extremely difficult to implement mandated tasks," Mood told reporters after a closed-door meeting Tuesday with the United Nations Security Council.
Mood said there are men, women and children trapped by fighting, and suffering by civilians is getting worse, the U.N. News Center reported.
He said U.N. monitoring will not resume until there is a significant reduction in violence, as well as a commitment by both the Syrian government and the opposition to the observers' safety, security and freedom of movement.
"The government has expressed that very clearly in the last couple of days. I've not seen the same clear statements [from] the opposition yet," Mood said.
The observer mission was established in April to monitor the cessation of violence in Syria, as well as support the full implementation of a six-point peace plan put forward by U.N.-Arab League envoy Kofi Annan that calls for an end to violence, access for humanitarian agencies to provide relief to those in need, the release of detainees, the start of inclusive political dialogue that takes into account the aspirations of the Syrian people, and unrestricted access to the country for the international media.
U.N. peacekeeping head Herve Ladsous told reporters the six-point plan remains the only way for finding a solution to the Syrian crisis, which has claimed the lives of more than 10,000 people since the uprising against President Bashar Assad began last year.
"There is no other plan, no other game in town -- there's no 'plan B,'" Ladsous said.