"It is well known that Syria and Iran are pushing at this time for the destabilisation of the government of Fouad Siniora," the French diplomat told the LCI television station.
Douste-Blazy's comments come the day after the head of Lebanon's powerful movement Hizbullah urged his supporters to prepare street protests to topple the anti-Syrian government, which is beset by political crisis.
Earlier this month France said that it saw no evidence of a co-ordinated attempt to unseat the Lebanese government, but warned nonetheless against any such attempts, affirming its strong ties with Beirut.
"I do not think that there is a war between Israel and Lebanon," Douste-Blazy said. "I think that Syria, Iran and Hizbullah are trying to destabilise Lebanon, which is our friend."
The US government has pointed to what it says is "mounting evidence" that Hizbullah has been preparing plans to unseat Siniora's government with the help of Iran and Syria. Damascus has rejected the allegations.
The Siniora government has been in crisis since the resignation earlier this month of six pro-Syrian cabinet ministers, including two from Hizbullah, which has sought to gain political ground after its self-declared "victory" over Israel in a month-long summer war.
The pro-Damascus politicians are demanding a greater voice in the government, which has been dominated by an anti-Syrian coalition since elections last year.

Copyright AFP (Agence France-Presse), 2006