STATE DEPARTMENT - Syria said Tuesday it accepts a cease-fire plan proposed by the United States and Russia that would begin Saturday.
A Syrian government statement said the military will continue its operations against Islamic State and al-Qaida-linked groups.
The U.S.-Russia plan also does not apply to those militants, and any other groups have until Friday to confirm their participation.
The main Syrian opposition High Negotiations Committee said late Monday it agrees to the cease-fire as long as its demands for the lifting of sieges, delivery of humanitarian aid, and an end of bombings of civilians are met.
In a joint statement Monday, the U.S. and Russia said that under the plan parties involved in the conflict would limit any use of force to situations such as responding in self defense. The parties would also agree to provide unhindered access to humanitarian groups delivering aid to besieged areas.
The U.S. and Russia are co-chairs of a cease-fire task force that is part of the 17-nation International Syria Support Group. The group met in Munich earlier this month and had hoped to implement an initial cease-fire plan by last Friday.
Some of the issues linked to the cessation still appear to be unresolved.
U.S. State Department spokesman Mark Toner said over the next few days, the task force will work out standard operating procedures.
He also said the group may rely in part on non-government organizations and journalists in Syria for reports on possible cease-fire violations.
“No one is denying that this is going to be a challenging environment to monitor,” said Toner.
The group is also seeking assurances from the Syrian government, the opposition and other parties involved in the conflict.
"Over the coming days, we will be working to secure commitments from key parties that they will abide by the terms of this cessation," said U.S. Secretary of State John Kerry.
In an interview with Al Arabiya, Syrian opposition leader Khaled Khoja expressed concern that the Syrian government could use the presence of al-Nusra terrorists as a pretext to continue hitting rebel targets in areas near the terrorist group.
Earlier, the White House said President Barack Obama and Russian Leader Vladimir Putin spoke by phone Monday to discuss the plan.
The White House said Obama emphasized that the priority was to ensure “positive responses” by the Syrian regime and the armed opposition.
“Russian and American military will jointly define the territories on the map where such groups are active,” said Putin.
Word of the potential truce comes a day after Islamic State militants claimed responsibility for a series of attacks in Damascus and Homs that left over 100 people dead.
Toner, of the State Department, condemned the attacks and said it would take a "united and global effort to destroy this terrorist organization."
Russia's Foreign Ministry said in a statement the terror attacks need an adequate reaction from the international community.
A U.N. spokesman said Secretary-General Ban Ki-Moon welcomed the cease-fire plan and "strongly urges" all parties to abide by terms of the agreement.
U.N.-facilitated talks between the Syrian government and opposition broke off earlier this month, partly due to opposition concerns about the Russian-backed Syrian government's continued bombings around Aleppo.
U.N. envoy for Syria Staffan de Mistura initially planned to resume talks by February 25, but last week, the U.N. announced the talks would be further delayed.
Russia's airstrikes have been blamed for increasing the war's toll on Syrian civilians, prompting more of them to leave their homes as refugees and try to flee across the border into Turkey.
UNICEF welcomed word of a cease-fire plan Monday, which could allow relief organizations to expand deliveries of aid.
“If implemented, a cessation of hostilities represents an opportunity to begin the work of repairing a country that has suffered far too much for far too long,” said Anthony Lake, the agency’s executive director.
VOA White House correspondent Mary Alice Salinas and Chris Hannas in Washington contributed to this report.