More than 100,000 people have now been killed in the Syria civil war, UN leader Ban Ki-moon said Thursday as he appealed for new efforts to convene a peace conference.

On the ground, violence raged in the flashpoint city of Homs and a car bombing in Damascus killed 10 people, the Syrian Observatory for Human Rights said.

The UN chief and US Secretary of State John Kerry told reporters at the United Nations that there could be no military solution to the 28-month-old conflict.

The Britain-based Observatory has previously reported that the death toll had crossed the 100,000 threshold.

On Thursday, Ban said: "More than 100,000 people have been killed, millions of people have either been displaced or become refugees in neighbouring countries.

"We have to bring this to an end. The military and violent actions must be stopped by both parties, and it is thus imperative to have a peace conference in Geneva as soon as possible."

The United States and Russia vowed in May to press for a follow-up to a peace conference held in Geneva last year, which set out a transition plan.

However, divisions in the international community and disagreements between the Syrian regime and opposition about the goals of such a conference have blocked efforts.

Syrian National Coalition president Ahmad Jarba was in New York on Thursday for talks with Kerry ahead of a Friday meeting with UN Security Council envoys.

Kerry said there are "enormous levels of suffering".

"There is no military solution to Syria, there is only a political solution. That will require leadership in order to bring people to the table," he added.

Kerry said he spoke on Wednesday with Russia's Foreign Minister Sergei Lavrov.

"We remain committed to the effort to bring the parties to a Geneva II, to implement Geneva I, and we will try our hardest to make that happen as soon as is possible," he said.

Ban has previously said he would like a peace conference in September. But UN diplomats say the conflict is now so bitter that they doubt the two sides can be brought to the negotiating table.

"The chances of a meaningful peace conference are now zero, but the US and UN can't admit that," said Richard Gowan of New York University's Center for International Cooperation.

US President Barack Obama's plan to provide vetted Syrian rebels with weapons and strategic military aid is gaining traction in Congress, according to US lawmakers.

Washington is currently providing humanitarian and non-lethal military aid to rebel groups.

The US government promised an expansion of military aid to Syria's rebel forces in June after accusing President Bashar al-Assad's forces of using chemical weapons, but such aid has yet to be disbursed.

Ban also said that two UN envoys had completed talks in Damascus on seeking access for UN inspectors for an inquiry on the use of chemical weapons in Syria.

Ake Sellstrom, head of the inquiry, and Angela Kane, the UN high representative for disarmament, arrived in Damascus on Tuesday.

"They are coming out of Syria now, we will get the report soon," Ban said.

On the ground, the fighting was intense, especially around rebel areas of Homs in central Syria, which the army has besieged for more than a year, said the Observatory.

Homs-based activist Yazan said the current army offensive was entering its fourth week, and added that for the second time this week, the historic Khaled Bin Walid mosque was hit by regime shelling.

The Syrian Observatory said a car bomb attack in Jaramana, a Christian-Druze suburb of Damascus, killed 10 people. State television had earlier reported a toll of seven dead.

Thursday's violence comes two weeks into the Muslim fasting month of Ramadan. During this fortnight alone, at least 2,014 people, mostly combatants, have been killed in the conflict, the Observatory said.

More than 1,323 of the dead were pro- and anti-regime fighters, it said.

The toll for combatants killed has spiked "because the intensity of the fighting is escalating", Observatory director Rami Abdel Rahman told AFP.