Updated

U.N. envoy Kofi Annan said Friday that Iran should be involved in efforts to end the escalating violence that has claimed thousands of lives and forced hundreds of thousands from their homes.

Annan, the joint U.N.-Arab League envoy, told reporters that he is working to convene a so-called 'contact group' meeting on Syria in Geneva on June 30. The United States has vehemently opposed the involvement of Iran demanded by Russia. Annan said the composition of the meeting is one of the sticking points that may not be resolved until next week.

"I have made it quite clear that I believe Iran should be part of the solution," the former U.N. secretary-general told reporters in Geneva, flanked by Maj. Gen. Robert Mood, the head of the struggling U.N. observer mission in Syria.

Annan said it was "time for countries of influence to raise the level of pressure on the parties on the ground." However, he had no specific proposals for changing his six-point peace plan, which he said Syria had not yet implemented but still might support in the future.

"The longer we wait, the darker Syria's future becomes," Annan said.

Mood praised the work of his 300 U.N. monitors, whose mandate ends next month. He conceded, however, that they are now largely confined to bureaucratic tasks and calling Syrians by phone because of the insecurity and dangers on the ground.

"They are keen to resume their work. Their commitment to the Syrian people has not faltered," he emphasized. "Whether more observers or arming observers would be relevant to the situation on the ground, I'm far from convinced that that would help the situation on the ground."

The increasing militarization of both sides in the conflict has Syria lurching toward civil war. The failure of Annan's internationally brokered peace plan has made it more difficult for outside observers, humanitarian workers and supplies to get in, or reliable information to filter out.

Activists say more than 14,000 people have been killed since the uprising against President Bashar Assad's regime began in March last year. U.N. officials said Friday that an agreement by Syria to allow in aid workers and supplies to four of the hardest-hit provinces has been delayed by the steady violence.

So far, only reconnaissance missions to prepare for the aid workers and supplies have been conducted, U.N. humanitarian officials said.

In Moscow, Russian Foreign Minister Sergey Lavrov said that Moscow's arms supplies to Syria fully conform to international law. Lavrov said he would tell U.S. Secretary of State Hillary Rodham Clinton at their meeting set for next week that Russia sees no need to justify its action.

Clinton issued a harsh reprimand to Russia last week, saying that Moscow "dramatically" escalated the crisis in Syria by sending attack helicopters there. The State Department acknowledged later that the helicopters were actually refurbished ones already owned by the Syrian regime.

Russia has continued to provide Syria's government with weapons despite its violent crackdown on a popular uprising that began in March 2011.