Members of the Syrian opposition have expressed caution in advance of an upcoming Friends of Syria meeting in Istanbul.
The gathering will be hosted on Saturday by Turkey and more than 10 ministers, including US Secretary of State John Kerry, are expected to attend.
Delegates will discuss ways to bring an end to the two-year-old conflict in Syria.
The former president of the Syrian National Council, Abdelbaset Sieda, said previous Friends of Syria meetings have not produced results.
"We always hoped that it would result in concrete decisions and actions. But so far, we've only received promises of support without any action," he said.
"We really hope to get real support, of all kinds, especially in terms of means of protection for the Syrian people against continuous killings," Sieda added.
The Friends of Syria concept was formed by Western and Arab countries that support opposition to Syria's President Bashar Assad.
Its core group includes the US, Britain, France, Germany, Egypt, Saudi Arabia, the United Arab Emirates, Turkey, Qatar and Jordan.
It has held several meetings hosted by various countries, the last one in December in Morocco, where members announced a humanitarian fund for Syrians, including $100m from Saudi Arabia and a fund to be managed by Germany and the United Arab Emirates for the reconstruction of the country.
Plea for military aid
Opposition members have repeatedly asked for increased military assistance.
"The reality is we never got the type of help that we would like to get. They (Friends of Syria) are helping us on their own terms, focusing on humanitarian aid and things that would not help us on the ground win the war with the regime," Saleh Mubarak, an opposition figure, said.
In-depth coverage of escalating violence across Syria
Tensions within the opposition rose last month with the election of Ghassan Hitto as interim prime minister for the opposition.
Some of his critics claimed the Muslim Brotherhood orchestrated the choice of Hitto, a Syrian-born US citizen and a little-known figure prior to his election.
Some rebels say the Brotherhood is trying to control the uprising through the political opposition's exiled groups, marginalising fighters inside the country from non-Islamist groups.
Government official killed
As the opposition awaits military assistance, violence continued in Syria.
A Syrian activist group has said armed men shot and killed a government official in a Damascus restaurant.
The Britain-based Syrian Observatory for Human Rights (SOHR) says Ali Ballan, head of public relations at the Ministry of Social Affairs and a member of Syria's relief agency, was killed late on Thursday.
The group, which relies on a network of activists in Syria, said the shooting occurred in the western neighborhood of Mazzeh.
It gave no further details on Friday.
US troops in Jordan
On the diplomatic front, Russia once again criticised US over Syria policy.
Alexander Lukashevich, Russian foreign ministry spokesman, called the deployment of US troops in Jordan over the Syria crisis an unconstructive step that threatens to expand the conflict.
He said such a move ran counter to internationally-agreed principles for ending the crisis through negotiations.
"These are absolutely not the actions that we now need to bring Syria out of its dead end," Lukashevich told reporters.
"These actions exacerbate the Syria crisis, which is now gaining the dimensions of a regional crisis," the spokesman added.
Chuck Hagel, US defence secretary, revealed on Wednesday that 150 US military specialists had been deployed in Jordan since last year and that he had ordered the army to bolster the mission by bringing the total American presence to more than 200 troops.