The United States is open to "helpful" Iranian input during an upcoming peace conference in Switzerland aimed at ending Syria's war, U.S. Secretary of State John Kerry said on Sunday.

"We're happy to have Iran be helpful," he told reporters in Jerusalem.

Switzerland on Wednesday assumed the rotating chairmanship of the Organization for Security and Co-operation in Europe, naming the Western Balkans and South Caucasus as its priorities.

During its year at the helm of the 57-member body, Switzerland vowed to make a "tangible contribution to fostering security and stability, improving people's lives and strengthening the OSCE's capacity to act".

Invitations to a Syria peace meeting in Switzerland next month have not been issued as planned because of delays in the formation of an opposition delegation, a Syrian newspaper said Tuesday.

"An official source at the foreign ministry said that invitations to attend the 'Geneva 2' conference were not sent out as planned on December 28th," reported the Al-Watan newspaper, which is close to the Syrian regime.

Switzerland said Monday it had granted a three-month visa to Kremlin critic Mikhail Khodorkovsky, who has been staying in a German luxury hotel since his release from a Russian prison.

Khodorkovsky, a former oil tycoon, was jailed for 10 years for financial crimes but pardoned over a week ago by President Vladimir Putin in a deal that Germany helped broker behind the scenes.

At least four skiers died and two others were critically injured as avalanches hit the French and Swiss Alps after heavy snowfalls and relatively mild temperatures, police said Friday.

Near the Swiss resort of St. Moritz an off-piste skier of unidentified nationality was swept away by an avalanche on the slopes of the Piz Nair.

A helicopter crash in central Switzerland on Saturday hurt the pilot and four other occupants -- but a seven-year-old child on board escaped uninjured, police said.

Two of the occupants -- the mother of the child and a flight assistant -- were severely hurt in the accident, which occurred as the 45-year-old pilot was attempting to land the helicopter in a parking lot on a military-owned field in the canton of Glaris.

A French report ruling out poisoning in Yasser Arafat's 2004 death has a glaring inconsistency, the co-author of a Swiss probe said Thursday, sticking by his team's conclusion that the Palestinian leader was likely killed.

"Our data lean more towards the thesis of poisoning than in the opposite direction," Professor Francois Bochud, head of the Lausanne Institute of Applied Radiophysics, told AFP.

A Swiss magazine said Thursday it had spent 24 hours snooping on the Alpine country's intelligence boss to give spies a taste of their own medicine.

Stefan Howald, deputy editor of the left-wing weekly WochenZeitung (WOZ), said it had managed to gather a raft of private information about spy-in-chief Markus Seiler.`

Swiss Foreign Minister Didier Burkhalter was Wednesday elected president of the Alpine country for 2014, taking over from Defense Minister Ueli Maurer.

The Swiss presidency rotates every year between the seven members of the country's cross-party cabinet, with the role of the head of state largely symbolic.

A local deputy from Switzerland's populist Geneva Citizens' Movement (MCG) was excluded from the regional party on Friday for appearing to support the destruction of Israel.

Denis Menoud wrote on his Facebook page Tuesday that following Iran's historic nuclear deal with the West, "the key thing is that Israel is on the path to being incinerated."