The United Nations has been pushing the talks that it hopes will end a conflict that has been exploited by jihadists and sent tensions between Iran and its Gulf rivals soaring.
More than 6,400 people have been killed and almost 2.8 million displaced since a Saudi-led coalition began operations in March 2015 against Iran-backed rebels who have seized swathes of territory, including the capital Sanaa.
The talks were originally supposed to start on Monday but were delayed after the rebels failed to show up in protest against what they described as Saudi violations of a ceasefire, in effect since April 11.
Insurgents have sent representatives from the Shiite Huthi group and members of former president Ali Abdullah Saleh's General People's Congress party.
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A member of the Yemeni government delegation confirmed that the talks were to open at 1600 GMT.
President Abedrabbo Mansour Hadi had sent a message to UN envoy Ismail Ould Cheikh Ahmed demanding the "negotiations open today evening" and rejecting "rebel conditions to modify the agenda agreed on," according to a member of the government delegation.
Mahdi al-Mashat, a representative of rebel leader Abdulmalik al-Huthi, said yesterday that the rebels had been assured that the agenda for the talks would be "clear and tackle issues that could help achieve peaceful solutions".
Writing on Facebook, Mashat warned however that "we will have the right to suspend our participation" if the assurances are not met.
Diplomats say that rebels are demanding an end of the Arab coalition operations and a naval blockade on Yemen that began more than 13 months ago.
Saudi ally Turkey said today that it has frozen assets belonging to Saleh and his son, in line with the sanctions.
Saleh amassed billions of dollars through corruption and stashed assets in at least 20 countries during his 33 years in power, according to a UN report released last year.