"We are going to start a new initiative with those countries that stand by the people, not the Syrian government. We are preparing this," Erdoğan told a meeting of his ruling Justice and Development Party (AK Party) in Ankara, giving no further details on the move.
"The process that occurred at the United Nations in relation to Syria is a fiasco for the civilized world," he said.
On Saturday, China and Russia stymied U.N. action on Syria by vetoing an Arab-backed Security Council resolution, the only members of the 15-member world body to vote against it, drawing widespread condemnation from Western and Arab nations.
Without naming any particular country, Erdogan said the vetoes gave a "green light" to the Syrian government to continue its military attacks on anti-government protesters. Assad's forces are also now battling armed insurgents in some areas.
"The UN Security Council has once again held captive the conscience of the international community. Possessing the power to veto is a great responsibility. Using this power gives a green light for the persecution to continue," Erdoğan said.
Turkish Foreign Minister Ahmet Davutoğlu was expected to travel to the United States on Wednesday for talks with US Secretary of State Hillary Clinton.
Clinton said on Sunday the United States would work with other nations to try to tighten sanctions against Syrian President Bashar al-Assad's government and deny it arms in the absence of a UN resolution.
US officials have said they were now gauging the prospects for a group of like-minded countries to coordinate support for Syria's political opposition, a move that could bypass Russian and Chinese resistance to anti-Assad measures.
Such an undertaking might be modelled loosely after the contact group that oversaw international assistance to rebels that overthrew Libyan dictator Muammar Gaddafi last year.
A senior Turkish foreign ministry official told Reuters it was "natural" to start discussing a plan for Syria outside a U.N. framework but it was too early to say whether the nations would set up a Libya-style contact group.
"Because of the veto we are in a situation where there are other options. We have to consider these carefully. It is too early to say we are headed towards a contact group as with Libya but of course, these need to be discussed," the official said on condition of anonymity.
He said Turkey was also awaiting the outcome of talks in Syria on Tuesday between Assad and Russian Foreign Minister Sergei Lavrov, who was expected to press the Syrian leader to end the violence and carry out reforms.
His visit came as Syrian forces renewed their bombardment of Homs, a city that is a hotbed of protests and rebels.
Once a staunch ally of Assad, Turkey has now strongly condemned his government's bloody crackdown and called for the Syrian leader to step down.
Turkey also hosts opposition members from the Syrian National Council and has given refuge to Syrian army defectors. Thousands of Syrian refugees fleeing violence at home have also taken shelter inside Turkey.