The U.S. and Russia successfully reached a deal Thursday with other permanent members of the Security Council that would hold Syrian President Bashar Assad’s regime responsible for the Aug. 21 chemical weapons attack in the Damascus suburbs that left more than 1,400 dead. 

But on Friday, the U.N. said chemical or biological weapons might have been deployed three more times after the Aug. 21 attack.

U.N. officials in Syria say in the next few days, they will investigate incidents reported just days after in Bahhariyeh Aug. 22, in Jobar Aug. 24, and in Ashrafiah Sahnaya Aug. 25. 

Altogether, seven incidents were reported this year where chemical weapons might have been used. The three earlier events happened in March and April. 

Inspectors plan to launch their investigation by Tuesday and hope to have a report completed by late October, the United Nations said. 

The Aug. 21 attack prompted the Obama administration in late August to threaten military force on Syria.

President Obama, as he held off with executing an operation himself, warned if Syria used weapons again, he would launch an attack without Congress’s approval. 

Just as Congress faced a vote on attacking Syria, Russia proposed a diplomatic alternative. As a result, Syria agreed to relinquish its chemical weapons arsenal and promised to sign the chemical weapons convention. 

Security Council members are expected to vote on a resolution Friday evening that outlines how Syria must hand over its chemical weapons to the international community. 

The measure doesn’t include authorization for a military strike if Syria fails to meet those guidelines. 

Sen. Bob CorkerRobert (Bob) Phillips CorkerPoll: Dem leads by 3 points in Tennessee Senate race GOP anxiety grows over Trump’s Iran decision Trump backs Renacci in Ohio Senate race MORE (Tenn.), the top Republican on the Senate Foreign Relations Committee, said Friday he's not satisfied with that caveat. 

"While we all want a verifiable diplomatic solution to Syria’s chemical weapons, the lack of enforcement measures makes me highly skeptical of Russia’s willingness to impose real consequences on Syria for non-compliance," he said in a release. 

"As Syria is given a chance to fulfill its obligations, it’s important that we reinforce our broader national interests for stability in Syria and reassure our allies of U.S. resolve to counter other threats, especially from Iran."