The United States on Wednesday warned of new international measures to halt Syria's bloody crackdown on protests after reports that more than 200 people had been "massacred" in two days.

The White House said if Damascus did not fully implement an Arab League plan to contain the violence, "the international community will take additional steps to pressure the Assad regime to stop its crackdown."

Syrian Vice President Farouq al-Sharaa is to hold talks with Russian officials in Moscow in a bid to defuse the crisis in his country, Russian news agencies quoted a Kremlin source as saying Friday.

"He is to be received in Moscow for a serious conversation," said the source, who was not identified. "This is our contribution to a solution to the crisis, which of course is worrying us."

Iran's parliament on Tuesday passed a bill for a free trade agreement with Syria in a show of support for President Bashar al-Assad's regime beset by protests and international pressure.

The bill provides for free trade between Iran and Syria within the next five years, according to Iranian state television.

Syria on Friday appealed to the international community as well as Arab countries to help it find an "honorable exit" to the crisis it is facing, notably by stopping the flow of weapons into the country.

"We are appealing to the outside world and our brothers in the Arab world to help Syria (prevent the) channeling (of) weapons" into the country, foreign ministry spokesman Jihad Maqdisi told a news conference in Damascus, speaking in English.

U.N. chief Ban Ki-moon on Thursday hit back at criticism from Syria's President Bashar al-Assad, insisting that information on the number of deaths in the government crackdown is "very credible."

Ban told reporters during a trip to the Dadaab refugee camps in Kenya that he could not believe that less than 4,000 people had been killed, as Assad's government has claimed.

U.S. Secretary of State Hillary Clinton on Thursday warned Internet firms to avoid offering the "tools of oppression" to authoritarian Middle East regimes trying to crush democracy protests.

Clinton urged private companies to "embrace (their) role in protecting Internet freedom" and ensure protection of ordinary people as well as political activists.

Lebanese Democratic Party leader MP Talal Arslan, accompanied by a religious Druze delegation, on Thursday held talks in Damascus with Syrian President Bashar al-Assad.

Addressing the Lebanese delegation, Assad said that “Syria is strong thanks to its people and the support of the brotherly and friendly people,” according to Syria’s state news agency SANA, stressing that “Syria is capable of overcoming the current events and that it won't ever give up its stances, principles and sovereignty whatever the pressures may be.”

Syria faced new sanctions after flouting Sunday an Arab League deadline to accept observers to monitor the unrest sweeping the country, which the U.N. says has killed more than 4,000 people.

A senior Qatari official said Damascus had asked for "new clarifications and further amendments to be made to the protocol which was proposed" to cover the deployment of the observer mission.

Syrian President Bashar al-Assad threatens to "fan the flames" of sectarian conflict not only in Syria but in the wider region, U.S. Vice President Joe Biden said in talks with the Turkish president, a U.S. official said Saturday.

"Assad and his regime are the source of instability in Syria now and pose the greatest danger to fanning flames of sectarian conflict not only in Syria but beyond," Biden told Abdullah Gul when they met Friday, the senior official told reporters.

The European Union will tighten sanctions against Syria's oil and financial sectors this week to punish the regime over its crackdown on protesters, a European diplomat said Monday.

EU foreign ministers meeting Thursday will adopt a raft of sanctions including bans on exporting gas and oil industry equipment to Syria, trading Syrian government bonds and selling software that could be used to monitor Internet and telephone communications, the diplomat said.