The Obama administration is preparing to explicitly demand the departure of Syrian President Bashar Assad and hit his regime with tough new sanctions, U.S. officials said Tuesday as the State Department signaled for the first time that American efforts to engage the government are finally over.

The White House is expected to lay out the tougher line by the end of this week, possibly on Thursday, according to officials who said the move will be a direct response to Assad's decision to step up the ruthlessness of the crackdown against pro-reform demonstrators by sending tanks into opposition hotbeds.

Egyptian Foreign Minister Mohammed Amr on Tuesday said he feared that revolt-hit Syria was "heading to the point of no return" and called for an immediate end to violence, the official news agency MENA reported.

"Egypt is following with extreme concern the dangerous deterioration of the situation in Syria," Amr said, expressing "his concern that the situation in Syria is heading to the point of no return," MENA reported.

The head of Iran's parliament's foreign affairs committee accused the United States of seeking to destabilize Syria after talks on Tuesday in Cairo with Arab League chief Nabil al-Arabi.

Alaeddin Borujerdi's visit to Cairo was the first since former president Hosni Mubarak resigned in February after 18 days of massive streets protests.

India, Brazil and South Africa said they are launching a mission to Syria on Wednesday in a bid to halt a deadly crackdown on anti-regime protests.

The governments of the three nations, under an initiative of the IBSA forum of emerging economies, are seeking to help open a dialogue between Syrian authorities and the public to help bring months of brutal violence to an end, a Brazilian foreign ministry spokesman told Agence France Presse on Tuesday.

Syrian President Bashar al-Assad promised on Tuesday an unceasing battle against the "terrorist groups" that his regime has accused of responsibility for the deadly violence that has wracked Syria since March.

"We will not waver in our pursuit of terrorist groups," Assad told visiting Turkish Foreign Minister Ahmet Davutoglu, according to state news agency SANA.

Russia on Tuesday reaffirmed its call for an end to violence and the launch of deep-rooted political reforms in Syria, during a phone call between the two countries' foreign ministers.

Foreign Minister Sergei Lavrov told his Syrian counterpart Walid Muallem that Moscow wanted to see the launch of "a broad Syrian dialogue" that could help the country find its own way out of the crisis, a Russian statement said.

The European Union has slapped further sanctions on the regime of Moammar Gadhafi, targeting two "economic entities" linked to the Libyan strongman, France said Tuesday.

The measures decided Monday "reinforce the system of international sanctions" already in place against Gadhafi's regime, foreign ministry spokeswoman Christine Fages told reporters.

Tunisia has fired its public prosecutor after a senior ally of the ousted Ben Ali regime was able to leave the country despite facing criminal investigations, the justice ministry said Tuesday.

Justice Minister Lazhar Karoui Chebbi had found incompetence on the part of Nejib Maaoui and decided he had to be replaced, a ministry spokesman said.

The speaker of Iraq's parliament on Tuesday called for an end to Syria's deadly crackdown on anti-regime protests, saying the neighboring country must "stop the bloodshed."

"The bloody events occurring in Syria call for us to demand that the Syrian government stop the bloodshed, because the government is responsible for protecting the people," Osama al-Nujaifi said in a statement.

Five members of Iran's security forces including an officer were killed when their vehicle was ambushed by "terrorists" in northwestern Iran, a local official told Fars news agency on Tuesday.

"Five police personnel were martyred... when their vehicle was destroyed" in West Azerbaijan province at midday on Monday, the city of Maku's governor, Hamid Ahmadian, told the agency.