US Secretary of State Hillary Clinton on Tuesday urged Syrian President Bashar al-Assad to plan a political transition in his violence-plagued country.

"We do believe that it is not too late for the al-Assad regime to commence with planning for a transition, to find a way that ends the violence by beginning the kind of serious discussions that have not occurred to date," Clinton told reporters after meeting with Haitian Prime Minister Laurent Lamothe.

She said Washington is trying to work with its "like-minded friends" to continue pressuring the Syrian government and pushing for humanitarian relief, as the flow of refugees is increasing with intensifying fighting between government and opposition forces.

Besides, the United States is working outside the UN Security Council to send "a clear message of support" for the Syrian opposition. She said Washington is providing nonlethal assistance to the opposition including communication and medical supplies.

"We have to work closely with the opposition because more and more territory is being taken, and it will eventually result in a safe haven inside Syria, which will then provide a base for further actions by the opposition," she said.

She urged the opposition to start working on "interim governing entities," set up humanitarian response efforts and safeguard the chemical and biological weapons stockpiled in Syria.

The conflict in Syria has entered its 17th month and fighting has raged for days in the capital of Damascus and Aleppo, the second largest city in the country.

Assad appointed five security officials on Tuesday, a week after a bomb ripped through a high-level meeting and killed four security officials from Assad's inner circle, which hit the Syrian administration to the core.

The Syrian army continued hunting "terrorists" in major cities, causing big losses among them while many of them surrendered themselves to the authorities, according to state-run SANA news agency.

It also said the Syrian troops pursued defeated armed terrorist groups at Nahr Isha neighborhood in the capital of Damascus Tuesday.