More than 100,000 people have now been killed in more than two years of conflict in Syria, UN chief Ban Ki-moon said, as he appealed for new efforts to convene a peace conference.
Ban on Thursday called on the Syrian government and opposition to halt the violence, saying it was "imperative to have a peace conference in Geneva as soon as possible".
The secretary-general spoke before talks with US Secretary of State John Kerry, who stood nearby.
"There is no military solution to Syria,'' Kerry then told reporters. "There is only a political solution, and that will require leadership in order to bring people to the table."
Last month, the UN increased the overall death toll in the conflict to nearly 93,000, with civilians bearing the brunt of the attacks.
The conflict in Syria started with peaceful protests against four decades of the Assad family rule but turned violent in the face of a security crackdown.
The US and Russia are trying to convene an international conference in Geneva, along with the UN, to try to agree on a transitional government based on a plan adopted in that city a year ago.
Kerry said he talked to Russian Foreign Minister Sergey Lavrov on Wednesday and that both countries remained committed to bringing the warring parties together to further peace efforts.
"We will try our hardest to make that happen as soon as is possible,'' Kerry said.
Ban’s statement came hours after Syrian state media said that a car bomb explosition near the capital Damascus killed at least seven people and wounded 62.
SANA news agency said the bomb hit the al-Siyouf Square in the Jaramanah disctrict of the capital.
It blamed "terrorists", a term the Syrian government uses for rebels who are fighting a two-year-old civil war against President Bashar al-Assad.
Bombs have previously hit Jaramanah, a religiously mixed area that houses supporters and opponents of Assad but which is under army control.
After rebel gains around the country, the army has pushed back in recent weeks and reinforced the capital while rebels hold outlying areas. The fighters use mortars and car bombs to hit areas still held by the government.