An international media watchdog has criticized a UAE court decision to uphold a 10-month jail sentence for a user of microblogging website Twitter who posted about the trial of 94 Islamists.

Reporters Without Borders (RSF) also called for the immediate release of another man it said was arrested in the United Arab Emirates this month on similar charges.

Germany's foreign intelligence service believes Syrian President Bashar Assad's forces have gained strength, revising its prediction from last year of a quick regime collapse, a media report said.

Assad's forces are now able to keep the rebels in check, although victory remains elusive, according to a report by the service chief Gerhard Schindler, news site Spiegel Online reported.

Syria's main opposition group opened key talks Thursday in Istanbul to debate whether to negotiate with the regime on ending the bloody two-year civil war, as proposed by the U.S. and Russia.

During their three-day meeting, the Syrian National Coalition -- which is under fire from both its backers abroad and rebels on the ground -- is also expected to choose a new president, discuss expansion to include new members and decide the fate of an interim rebel government, opposition members told AFP.

U.S. Secretary of State John Kerry on Thursday admitted there was skepticism and cynicism about his efforts to broker new talks between Israelis and Palestinians, as he made his fourth visit to Israel.

Flying in from a night of diplomacy in Amman over the war in Syria, Kerry went straight into talks with Prime Minister Benjamin Netanyahu as he pursued his bid to kick-start negotiations frozen since late 2010.

World powers urged Syrian President Bashar Assad to commit to peace, but warned Thursday that if he fails to negotiate a political transition they would boost their backing of the opposition.

The stark warning came from a meeting of the Friends of Syria group, which held talks on Wednesday in Amman to try to agree the contours of a peace conference to end the war.

Middle East unrest increases the chance of Israel becoming embroiled in a surprise war, the head of its air force said on Wednesday.

"When you look (around) today I think that a surprise war can be born in very many configurations," Major General Amir Eshel told a conference near Tel Aviv in remarks broadcast on local television and radio.

French President Francois Hollande and British Prime Minister David Cameron Wednesday said they would seek European support for their proposal to arm the Syrian opposition to fight regime forces.

"We are prepared to lift the arms embargo further so that the opposition can present themselves as the legitimate voice of the Syrian people," Cameron told reporters during a brief stopover in Paris on the way back from Brussels.

Forty Syrian soldiers and pro-regime militiamen were killed in fighting with rebels on Wednesday around an army camp near the town of Nayrab in the northwestern province of Idlib, a watchdog reported.

"The fighting has killed 14 from the rebel side and not less than 40 among the soldiers of the regular army and members of the Popular Committees (pro-regime militia)," the Syrian Observatory for Human Rights said.

A Saudi court sentenced eight citizens to jail terms of between 10 and 25 years on Wednesday after convicting them of plotting for al-Qaida, state news agency SPA reported.

The eight were convicted of "forming a group to eliminate police officers, among them Colonel Mubarak al-Sawat" -- killed in 2005, SPA said.

Ansar al-Sharia spokesman Seifeddine Rais, detained in the Tunisian city of Kairouan at the weekend as police enforced a government ban on its annual congress, was released on bail on Wednesday, the Salafist group said.

"God be praised, our brother Seifeddine Rais has been freed," the group said on its Facebook page.