The U.N. Security Council will vote Saturday on a Western-drafted resolution allowing a ceasefire observer mission in Syria even though Russia's support is in doubt.

The United States called for the vote after a second day of wrangling with Russia over security guarantees for the first 30 unarmed military monitors who U.N.-Arab League envoy Kofi Annan wants in Syria early next week.

Syrian forces killed six people and shelled rebel areas of Homs on Saturday ahead of a U.N. Security Council vote on a Western-drafted resolution that would send observers to monitor a shaky truce now in its third day.

Forces loyal to President Bashar Assad killed four civilians as they opened fire at a funeral procession of a demonstrator in Aleppo, the Syrian Observatory for Human Rights said.

Iran is to present "new initiatives" at nuclear talks with world powers in Istanbul on the weekend, the official leading the country's negotiating team, Saeed Jalili, said on Wednesday.

"The Iranian delegation will have new initiatives and we hope that the other party will have a constructive approach," he told Iran's Arab-language network al-Alam, without elaborating.

France said on Tuesday that Syria was not implementing a U.N. and Arab League-backed peace plan after Damascus said it had started pulling troops out of certain provinces.

The Syrian claim was "a new expression of a flagrant and unacceptable lie" that "shows a degree of impunity against which the international community absolutely must act," foreign ministry spokesman Bernard Valero said.

Iran on Monday urged "honesty" at crucial talks with world powers due to be held this week in order to defuse a tense international showdown over its disputed nuclear activities.

"We hope the P5+1 will come to the negotiating table with honesty, and we also will make an honest effort so that both sides reach a win-win conclusion," Foreign Minister Ali Akbar Salehi told the Iranian parliament's website.

China on Monday urged Syria to honor its ceasefire commitment, after Damascus said it wanted guarantees from armed rebels before it pulled back its troops from protest hubs.

The Syrian army was scheduled to withdraw from protest cities on Tuesday under a peace deal brokered by former U.N. chief Kofi Annan, with a complete end to fighting set for 48 hours later.

The international mediator for Syria, Kofi Annan, said on Sunday he was shocked by the "unacceptable" surge in bloodshed there despite a U.N. deadline for a halt to all violence next week.

"I am shocked by recent reports of a surge in violence and atrocities in several towns and villages in Syria, resulting in alarming levels of casualties, refugees and displaced persons, in violation of assurances given to me," Annan said in a statement.

Syria said Sunday it will not withdraw its forces from protest hubs without "written guarantees" that the opposition will also lay down its arms, a demand swiftly rejected by rebels, who said they will not give guarantees to a regime they do not recognize.

"To say that Syria will pull back its forces from towns on April 10 is inaccurate, with (U.N.-Arab League envoy) Kofi Annan having not yet presented written guarantees on the acceptance by armed terrorist groups of a halt to all violence," the Syrian foreign minister said in a statement.

More than 100 people were reported killed across Syria on Saturday, 74 of them civilians, as regime forces pressed a protest crackdown three days ahead of a deadline to cease fire and pull back.

Monitors reported the escalation in violence despite U.N. chief Ban Ki-moon's latest rebuke to Damascus for stepping up its assault on dissent hubs ahead of Tuesday's deadline.

Syria lashed out at the U.N. high commissioner for human rights on Friday, accusing her of turning a blind eye to "terrorism" funded from abroad.

Citing a foreign ministry letter to Navi Pillay, state news agency SANA said her "bias against Syria has become evident as she turns a blind eye to terrorism targeting the Syrian people at the hands of armed groups with an external funding."