Yemen's government and its opposition are set to sign a deal on Monday for an orderly transition of power and end three months of violence that has claimed more than 130 lives, an official told AFP.
An official of the Gulf Cooperation Council (GCC), which brokered the agreement, said the two sides have been invited to Riyadh to ratify the deal.
"The delegations of the Yemeni government and the opposition will sign the agreement on Monday at a ceremony in Riyadh," the official in the Saudi capital said, asking not to be named.
Yemen's ruling party confirmed its representatives will attend.
"We have received an invitation from Saudi Arabia to sign in Riyadh an agreement on the Gulf Cooperation Council initiative," the deputy secretary general of Yemen's ruling General People's Congress, Sultan Al Barakani, said.
A leader from the Common Forum, a coalition of Yemen's parliamentary opposition, said a delegation from his group would also head to Riyadh on Wednesday to sign the agreement.
Barakani said the ambassadors of the United States, European Union members, GCC states and a UN representative in Riyadh will witness the signing.
The six-nation GCC had proposed the formation of a government of national unity in Yemen, President Ali Abdullah Saleh transferring his powers to his vice president, and an end to deadly protests rocking the impoverished country.
Under the GCC initiative, the president would submit his resignation to parliament within 30 days, with a presidential election being held within two months.
However, a defiant Saleh, who has ruled Yemen for 32 years, has publicly insisted on sticking to the constitution in any transfer of power, even though the General People's Congress has said it accepts the GCC plan.
Demonstrations demanding the immediate ouster of Saleh since late January have claimed the lives of at least 130 people.
The six GCC states as well as the United States and the European Union vouch for the implementation of the agreement, according to the text of the plan.
Opposition spokesman Mohammed Qahtan said the Common Forum told GCC secretary general Abdullatif Al Zayani of the decision to accept the transition.
"We have given our final accord to the (GCC) initiative after having received assurances from our Gulf brothers and American and European friends on our objections to certain clauses in the plan," he told AFP.
Washington has strongly backed the plan, while Britain on Monday warned that Yemen's "grave economic, social and security challenges" would escalate unless the transition from Saleh's rule was achieved quickly.
British Foreign Office minister Alistair Burt urged all sides to "seize this opportunity and finalise an agreement," adding: "The GCC initiative represents our best hope for a constructive and peaceful way forward."
Despite the Common Forum agreeing to the transition, demonstrators have kept up their agitation for Saleh's immediate ouster and trial.
At least six more people were shot and wounded in separate demonstrations in Yemen on Tuesday.
Violence erupted in the town of Taez, 200 kilometres (125 miles) south of the capital Sanaa. An organiser of the protest there, Ahmed Wafi, said three men were wounded, one seriously, when troops fired at demonstrators.
In Aden farther south, three people were wounded when security forces opened fire, witnesses and medical sources said.
Tens of thousands of people also kept up their sit-in at the main square in the capital and repeated their rejection of the transition plan.
"We totally reject this plan. We demand not only that President Ali Abdullah Saleh leave, but he should also be tried," one protester, Hashim al-Sufi, told AFP.
The more radical demonstrators, who have been observing a three-month sit-in at the square, on Tuesday called for a "march on the presidential palace."