"The United Nations are losing quite a lot of their credibility," Dogan news agency quoted Turkish President Abdullah Gul as telling journalists in Istanbul.
Gul spoke after Saudi Arabia -- like Turkey a staunch backer of the bloody war against the Syrian government -- rejected a Security Council seat one day after winning it.
"I understand that Saudi Arabia's decision aims to draw the international community's attention to this situation ... We must respect their decision," said Gul.
The Saudi foreign ministry said on Friday Riyadh would not be member of a body that has been unable to tackle long-standing Middle East conflicts.
Both Saudi Arabia and Turkey, along with Qatar, are three biggest supporters of the war in Syria which has killed more than 115,000 people since it started in 2011.
Turkey’s borders have been open to foreign-backed militants to pour weapons and more force, gathered from all over the world, into Syria to continue the insurgency which has been marked with extremely brutal and radical acts of killing and bloodshed.
Syria has repeatedly asked Turkey to close its borders to arms smugglers, but Ankara has never acted to do so.
Turkish Prime Minister Recep Tayyip Erdogan has repeatedly called for a reform of the 15-member Security Council to give Muslim nations more clout.
In addition to its five permanent members, the Council has 10 seats that are awarded for two-year periods by the General Assembly, which holds a vote every year for five of the seats.
Saudi Arabia was on Thursday chosen along with Chile, Chad, Lithuania and Nigeria.