Pederson said he told the Syrian government and opposition leaders and their supporters during his recent travels that "confidence-building is needed," cease-fires must be respected, terrorism must be fought and only a negotiated solution to the seven-year conflict is possible.
One of the key issues is building trust between Syrians, he said, and for this a change is needed on the ground "to be able to move forward."
He spoke in Geneva in his first meeting with reporters since taking up the post in January; a transcript was circulated to U.N. media in New York.
Pedersen said he hopes to build on the work of his predecessor Staffan de Mistura, saying his aim is "a negotiated outcome where two parties agree, with international support — and that will be the beginning for a new Syria."
De Mistura said at his last press conference in December that an "an extra mile" is needed to form a committee to draft a new constitution for the conflict-torn country because a list of participants submitted by Russia, Iran and Turkey has not been accepted by the United Nations.
Russia's U.N. Ambassador Vassily Nebenzia told reporters here this week that he expects the differences to be resolved.
Pedersen said he hoped a meeting of the constitutional committee "would then be the start of some serious discussions that could be the door-opener to a political process that will lead to a negotiated outcome for the conflict."
He said an agreement reached last October by Turkey, which backs the opposition, and Russia, which supports Syrian President Bashar Assad, avoided "a humanitarian disaster" in Idlib, the last opposition-held stronghold — "and I am pleased to see that the focus now is on finding a peaceful solution to the crisis."
Pedersen said control of the area by the al-Qaida affiliated group Hayat Tahrir al-Sham "is not something that can be sustained for the future," but he welcomed the commitment by Turkey and Russia to a peaceful solution.
U.N. experts said in a recent report that an unnamed U.N. member state estimated that Hayat Tahrir al-Sham has approximately 20,000 fighters in Idlib province and "remains the largest terrorist group in the country."