But in a worrying development ahead of the negotiations, government raids were reported to have killed five civilians in Syria's second city, Aleppo, despite a ceasefire.
The truce has prompted a nearly two-week lull in fighting between the Russian-backed regime and non-jihadist rebels since coming into force on February 27.
World powers are counting on the ceasefire to hold for a new round of indirect negotiations between the opposition and the government due to start on March 14 in Geneva.
The HNC said in a statement that its delegation would focus on creating a "transitional governance body with full executive powers".
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It insisted that President Bashar al-Assad "will have no place" in a future government.
A plan agreed by world powers last year called for six months of negotiations followed by a transitional government, a new constitution and elections within 18 months.
Assad's regime announced last month that it would hold parliamentary elections on April 13 instead, drawing criticism.
UN envoy Staffan de Mistura has said "substantive" talks will begin on Monday in Geneva and last no longer than 10 days.
"New elections... Should be held 18 months from the start of talks, that is from March 14," de Mistura told Russia's RIA Novosti state news agency today, in comments translated into Russian.
That would mean elections around mid-September 2017.
In addition to planning the polls, the focus of the Geneva negotiations will be on the formation of "an inclusive new government" and a new constitution, according to de Mistura.
"I hope that during the first stage of talks, we reach progress at least on the first question (of the new government), it doesn't matter whether this is on paper," he was quoted as saying.