"Reports indicate real improvement in the situation which reflects the parties' commitment to the cessation of hostilities," Ismail Ould Cheikh Ahmed said in a statement at the end of the fifth day of negotiations.
His remarks come a day after he spoke of "significant differences" between the Iran-backed Yemeni rebels and the government delegation who began negotiating on Thursday.
Ould Cheikh Ahmed said that a ceasefire coordination committee and local committees were "exerting extraordinary efforts to ensure the safety and security of Yemenis".
Since the delayed talks began on Thursday, the two delegations have been unable to reach a common understanding on how to firm up a ceasefire that went into effect on April 11.
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The delegations have agreed to appoint two officials, one from each side, to make recommendations on how to sustain the ceasefire, the UN envoy said.
The government delegation has insisted that the truce should include confidence-building measures such as opening safe passage to besieged areas and releasing prisoners.
Foreign Minister Abdulmalek al-Mikhlafi, who heads the government delegation, described the negotiations as "impotent" and accused the rebels of avoiding discussion of key issues.
Mikhlafi said on Facebook that the rebel delegation had backed down several times on proposals they had made.
The rebels have insisted that no ceasefire can be established without an end to coalition air strikes.
The coalition has said it reserves the right to respond to rebel violations of the ceasefire, with air strikes if necessary.
The government wants the discussions to start with the issue of a Huthi withdrawal from areas they have overrun, including the capital Sanaa, and their surrender of all heavy weaponry.