By Tom Miles, John Irish and Tom Perry
GENEVA/BEIRUT (Reuters) - Syrian rebels fought back against an offensive by government forces near a supply route into the city of Aleppo on Monday and said there had been no letup in Russian air strikes, despite a promise of goodwill moves by Damascus to spur peace talks.
U.N. envoy Staffan de Mistura was due later on Monday to meet Syrian opposition groups in Geneva, hoping to launch indirect peace talks after five years of war that has killed 250,000 people. A meeting with the government delegation was postponed because de Mistura had first to meet the opposition.
De Mistura pressed on with peace efforts as the death toll from an Islamic State suicide attack near Damascus climbed to more than 70 people, the Syrian Observatory for Human Rights said. The attack targeted a government-held neighborhood that is home to Syria's holiest Shi'ite shrine.
The Geneva peace talks mark the first attempt in two years to hold negotiations over Syria, whose war has drawn in regional and international powers and forced millions from their homes and into neighboring states and Europe.
The opposition to President Bashar al-Assad agreed late on Friday to travel to Geneva after saying they had received guarantees to improve the situation on the ground, such as a detainee release and a halt to attacks on civilian areas.
But the opposition says there has been no easing of the conflict since then, with government and allied forces including Iranian militias pressing offensives across important areas of western Syria, most recently north of Aleppo.
It is the first big government offensive for nearly a year in the Aleppo area, which controls access to opposition-held areas of the city from Turkey, a sponsor of the insurgency.
"The attack started at 2 a.m., with air strikes and missiles," said rebel commander Ahmed al-Seoud, describing the situation near Aleppo, parts of which are controlled by the government and parts are in opposition hands.
Seoud told Reuters his Free Syrian Army group had sent reinforcements to the area near the village of Bashkoy.
"We took guarantees from America and Saudi to enter the negotiations ... (but) the regime has no goodwill and has not shown us any goodwill," he said from nearby Idlib province.
The British-based Syrian Observatory for Human Rights said government forces were gaining ground in the area, and had captured most of the village of Duweir al-Zeitun near Bashkoy. It reported dozens of air strikes on Monday morning and Syrian state television said government forces were advancing.
NEGOTIATION "UNDER ESCALATION"
The opposition High Negotiations Committee (HNC) has indicated it will leave Geneva unless steps set out in a Dec. 18 Security Council resolution, endorsing peace moves including a lifting of sieges of blockaded areas, are implemented.
Bashar al-Jaafari, head of the government delegation, said on Sunday Damascus was considering options such as ceasefires, humanitarian corridors and prisoner releases. But he suggested they might come about as a result of the talks, not before them.
Opposition delegate Farrah Atassi said government forces were escalating their military campaign, making it hard to justify the opposition's presence in Geneva. Another opposition official highlighted heavy Russian bombardment of the northern Homs area on Sunday as one sign that nothing had changed.
"Today, we are going to Mr De Mistura to demand again and again, for a thousand times, that the Syrian opposition is keen to end the suffering of the Syrian people," Atassi said. "However, we cannot ask the Syrian opposition to engage in any negotiation with the regime under this escalation."
A senior Western diplomat said the opposition had shown up so as not to play "directly into the hands of the regime".
"They want tangible and visible things straight away, but there are things that realistically can't be done now such as ending the bombing. It's obvious that that is too difficult. The easiest compromises are releasing civilians and children."
The HNC was due to meet De Mistura at 5 p.m. (1600 GMT) at the U.N. headquarters in Geneva.
It also met him at a hotel on Sunday where a diplomatic source said they discussed a proposal by De Mistura to help meet their humanitarian concerns.
The diplomatic efforts have been beset by difficulties, including a dispute over who should be invited to negotiate with the government. Beyond that, the challenges are enormous and include lingering divisions over Assad's future.
TYPE OF GOVERNMENT
The Kurdish PYD party which controls large areas of northern Syria has been excluded in line with the wishes of Turkey, which considers it a terrorist group.
The HNC includes some of the foreign-backed rebel groups fighting Assad in western Syria. Islamic State is at war with both Assad and the rebels, and is fighting for its its own "caliphate" rather than a reformed Syria.
The United Nations is aiming for six months of talks that would focus on achieving a broad ceasefire, while also working toward a political settlement. The United States, which backs the opposition to Assad, has been urging the HNC to attend.
The Syrian government views all the groups fighting it as terrorists and instruments of foreign powers such as Saudi Arabia and Turkey.
Another complication is the type of government that will run Syria in any peace settlement. Jaafari said on Sunday Damascus favored an "enlarged national government", while the opposition want a transitional governing body.
(Additional reporting by John Davision in Beirut and Stephanie Nebehay in Geneva; Writing by Tom Perry, Editing by Timothy Heritage)