Indirect peace talks between Syria's warring parties are scheduled to resume in Geneva on Wednesday, the third round this year. There are two main groups at the negotiations in Switzerland, in addition to others that were invited by the United Nations as advisers.

The U.N. envoy for Syria says the talks this time are to focus on a political transition in the war-torn country, but chances for a breakthrough are slim as distrust and continuing disagreements between rival factions remain deep.

Here's a look at the talks:

BACKDROP OF VIOLENCE

The talks this week resume amid an escalation, with clashes underway mainly between government forces and militants, mainly near the northern Syrian city of Aleppo. The fighting could endanger a truce brokered by Russia and the United States that has mostly held since going into effect on Feb. 27. The first round of talks collapsed earlier in February amid a government offensive on Aleppo, Syria's largest city and once its commercial center. U.N. special envoy Staffan de Mistura said after talks with officials in Damascus earlier this week that keeping the truce was key, describing the cease-fire as fragile and stressing that all sides "need to make sure that it continues to be sustained."

MAIN PLAYERS

The main players are the Syrian government, which is backed by Iran, Russia and Lebanon's Hezbollah group, and the main opposition faction, the High Negotiations Committee or HNC, which includes groups that are backed by Turkey, Saudi Arabia and Qatar. The Islamic State group and al-Qaida's branch in Syria known as the Nusra Front are not taking part in the talks because they are opposed to negotiations and are considered terrorist organizations by the U.N.

WHO IS ATTENDING

The Syrian government delegation is headed by the country's ambassador to the U.N., Bashar Ja'afari, while the HNC's chief negotiator is Mohammed Alloush of the rebel group Jaysh al-Islam or Army of Islam. Other opposition groups are taking part in Geneva as well, including members of the internal opposition that has been tolerated by President Bashar Assad. All opposition groups other than the HNC were invited to Geneva by de Mistura as advisers so as not to anger the HNC, which considers itself the sole representative of the opposition.

MAIN POINTS OF DISAGREEMENT

The Syrian government delegation says the priority in the "proximity talks" should be on fighting terrorism while the HNC says the focus should be on setting up a Transitional Government Body with full executive powers in which Assad will have no role. The government says Assad was elected by the people and any talk about removing him from power is a red line. Over the past months, Syrian troops have captured wide areas from militants under the cover of Russian airstrikes. Syrian legislator and member of Assad's ruling Baath party Sharif Shehadeh says "the problem of the opposition is that it ... is still talking about a transitional government. This will not happen in Syria under any circumstances, even if this means prolonging the war for one hundred years."

WHO IS ABSENT

The Syrian Kurds, or rather, the Kurdish Democratic Union Party, PYD, and its military wing known as the People's Protection Units or YPG have not been invited to the talks. The U.S.-backed YPG has been the most effective force in fighting the Islamic State group in northern and eastern Syria. Although they consider themselves opposed to Assad, the HNC considers the PYD and YPG as pro-government. The Syrian Kurds' move to set up a federal region in northern Syria has angered both the government and the HNC.