Speaking on the long-awaited peace talks aimed at ending the war in Syria, Kerry said on Sunday that with militants infighting and al-Qaeda's growing strength things have become complicated for US to search for a political settlement of the conflict.

Kerry said Washington was relying on diplomacy to make an impact on the situation, citing plans for a peace conference next month in Geneva and efforts underway to eliminate the chemical weapons in the Arab country.

"No one really wants to go to war in Syria because it's a huge sectarian, you know, mess, with all kinds of implications," he said in an interview with ABC's "This Week."

"So you have to work with the tools that you have that are permissible. And that's exactly what we're doing, trying to make the most of the diplomatic tools available in order to be able to have an impact," he said.

Kerry acknowledged that in-fighting among the Syrian opposition and militant groups had left a void that is being filled by extremists and that entire sections of Syria are now safe havens for al-Qaeda.

"Yes, it's absolutely true. Al-Qaeda has greater clout there than it had before and it's an increasing threat. And it's a threat we're going to have to confront," he said.

The war in Syria started in March 2011, when pro-reform protests turned into a massive insurgency following the intervention of Western and regional states.

The unrest, which took in terrorist groups from across Europe, the Middle East and North Africa, has transpired as one of the bloodiest conflicts in recent history.

According to the United Nations, more than 120,000 people have been killed and millions displaced due to the turmoil that has gripped Syria for over two years.

SHI/SHI