Syrian President Bashar al-Assad has said his armed forces would try to retake the entire country "without hesitation", in an interview published after world powers agreed on a "cessation of hostilities".
Speaking to the AFP news agency, Assad said the involvement of regional players in the conflict meant "that the solution will take a long time and will incur a heavy price".
Syria war: Powers agree on 'cessation of hostilities'
He also rejected the UN's recent accusations that his regime is guilty of war crimes, calling the claims "politicised" in the interview that was conducted on Thursday in Damascus.
Earlier this week, international investigators said that several thousand prisoners have been executed, beaten to death or otherwise left to die during Syria's civil war, in policies that appear to amount to "extermination"under international law.
The mass scale of deaths of detainees suggests that the government of Syria is responsible for acts that amount to extermination as a crime against humanity," Paulo Pinheiro, the head of the UN-backed Commission of Inquiry on Syria, said on Monday.
'Nationwide cessation of hostilities'
Assad's interview was published hours after ministers from major international powers - including the US, Russia, Iran and Saudi Arabia - agreed to aim for a halt in hostilities in Syria within a week, as well as providing humanitarian assistance.
A UN task force kicked off its first meeting in Geneva on Friday as part of efforts to deliver aid in the besieged areas across Syria following the agreement in the German city of Munich.
"We have agreed on a nationwide cessation of hostilities," starting one week from now, US Secretary of State John Kerry said after the marathon talks in Munich.
Russian PM warns of world war if troops sent into Syria
"This will apply to any and all parties in Syria, except for Daesh (the Islamic State of Iraq and the Levant, or ISIL) and al Nusra," he added.
Importantly, the term "ceasefire" was not included in the plan - despite earlier calls from all sides for a more definite agreement.
Assad said that he supported negotiations to end the violence in the country, but added that the fight against what he called "terrorism" must continue.
"We have fully believed in negotiations and in political action since the beginning of the crisis; however, if we negotiate, it does not mean that we stop fighting terrorism," Assad said. "The two tracks are inevitable in Syria: first, through negotiations, and second through fighting terrorism."
But Saudi Arabia's Foreign Minister Adel al-Jubeir said on Friday that Assad must step aside to make it possible to defeat ISIL in Syria.
"Unless and until there is a change in Syria, Daesh will not be defeated in Syria," he said in Munich.
"When Assad goes, the fertile environment which Daesh operates in Syria will be removed."
Commenting on the interview, the US State Department spokesman Mark Toner on Friday said Assad was "deluded if he thinks that there is a military solution to the war in Syria".
Russian air strikes
Meanwhile, Russia continued its military campaign in support of Assad on Friday, just hours after the international call for a cessation of hostilities.
Fighting rages in Syria's Aleppo amid ceasefire talks
Activists told Al Jazeera that at least 18 people were killed on Friday in suspected Russian air strikes in the northern suburbs of Homs province.
Separately, at least three civilians were killed while 20 others were injured in suspected Russian air strikes in the suburbs of the capital Damascus, the UK-based Syrian Observatory for Human Rights reported on Friday.
In the city of al-Bab in Aleppo province, five children were killed in suspected Russian air strikes.
The conflict of almost five years has resulted in more than 250,000 Syrians being killed, has displaced millions more and sent hundreds of thousands fleeing as refugees to Europe.
Source: Al Jazeera and agencies