PAD coordinator Suriyasai Katasila said core leaders of the alliance have monitored the UDD's movements and they shared the view that the UDD rally could trigger violence.
He said the UDD leaders were pressing demands that are impossible to meet, which limits the chances of breaking the political impasse.
He said the UDD leaders' drive against what they call "a government system dominated by the bureaucrats" is only creating a false impression that they are fighting for democracy. In fact, the anti-government campaign was designed to serve the vested interests of the UDD leaders and particularly to help clear the name of former prime minister Thaksin Shinawatra, Mr Suriyasai said.
If the rally on Wednesday gets out of hand and degenerates into violence, the military could use this as an excuse to intervene, he said.
This would play into the hands of Thaksin and would only support his argument that the country remained undemocratic.
He said if the UDD did anything to provoke violence on Wednesday, the PAD would mount its own major rally.
The PAD was concerned the UDD would lead the country into chaos by holding rallies.
It could lay siege to important government places to force the government to bow to its demands - the tactics used by the PAD itself during its protests last year.
"If the UDD tries to do damage to the country or to establish a new system of government, the PAD is ready to make a move against it straight away," Mr Suriyasai said.
I guess that this only proves that the PAD think that they are a power unto themselves that can do what they want with impunity.
The hypocrisy is breathtaking.
I guess Suriyasai wasn't so concerned with violence when his underlings were shooting people, impaling people with spears, taking over government house and airports, and running over cops in the street.