Syrian opposition leaders say UN inspectors will have "unfettered" access to areas under rebel control to investigate the use of chemical weapons.
The Syrian National Coalition said in a statement on Friday it wanted the inspectors to go first to the town of Khan al-Assal, where an attack with chemical weapons was reported on March 19.
The announcement comes after the UN team, led by Swedish expert Ake Sellstrom, reached an agreement with Syrian President Bashar al-Assad's government to enter the country.
The coalition said it had sent a letter to UN Secretary General Ban Ki-moon to reaffirm "its offer of full co-operation with the investigation team, particularly in assuring their unfettered access into liberated areas.
"As the Free Syrian Army has recently liberated the Khan al-Assal area, we urge the UN team to begin its investigation in this area and hope to welcome their arrival without any further delays", it added.
UN inspectors are expected to go to Syria as early as next week to carry out inspections at three sites where chemical weapons attacks have been reported.
The United Nations says Khan al-Assal, which is near the key city of Aleppo, is one of the locations where the Syrian government has agreed to allow inspections.
It has said the other two sites are being kept confidential for safety reasons.
The Syrian government and the opposition blame each other for the Khan al-Assal attack.
UN inspectors only have a mission to determine whether chemical weapons have been used in the 28-month-old conflict, not who staged the attack.
The United Nations says it has been given reports on 13 suspected chemical weapons attacks during the war.
