United Nations envoy Staffan de Mistura's comments prompted criticism from some who said evacuations were not a solution.
That attack prompted the U.S.to carry out a rare strike against a Syrian military installation.
As President Bashar al-Assad's forces have rolled back rebels from territory they gained since the 2011 uprising began, hundreds of thousands of rebels and civilians have flooded into Idlib.
The warning does not seem to be holding back Damascus or its chief ally, Moscow.
On August 30, Russian Foreign Minister said during talks with Walid Muallem, Syrian Deputy Chairman of the Council of Ministers, Foreign and Expatriates Minister in Moscowб that Moscow warning the West not to play with fire in Syria.
Idlib is the largest remaining rebel stronghold.
Civil Defense workers and Syrian citizens gather after an airstrike hit a market in Maaret al-Numan in southern Idlib, Syria.
De Mistura floated two options: one to not accelerate military escalation to allow more time for talks, and another to "allow and facilitate a credible - credible - humanitarian corridor to allow the civilian population to temporarily evacuate to a safer area".
"I am once again prepared. personally and physically to get involved myself.to ensure such a temporary corridor would be feasible and guaranteed for the people so that they can then return to their own places once this is over", Staffan de Mistura told reporters in Geneva.
"Russia sees a cloud over Idlib, a cloud of terrorists". A movement of people could takes weeks or longer.
Russian Federation will begin a major naval exercise in the Mediterranean on Saturday, the Ministry of Defense announced, a move the Kremlin said was justified by a failure to deal with militants in Syria's Idlib province. The Kremlin agreed the drill may be connected with the situation in Syria's Idlib governorate.
The drills, scheduled to last a full week, will involve warships from Russia's Northern, Baltic and Black Sea fleets, the Caspian Flotilla, as well as Tu-160 missile-carrying bombers and Su-33 fighter jets, Tass said, quoting the defense ministry.
Over 25 Russian battleships and 30 warplanes will participate in military drills in the Mediterranean on September 1-8, the Russian Defense Ministry said Thursday, after Western countries threatened to bomb Syria again.
He's been meeting with his Russian counterpart in Moscow to discuss the offensive.
The drills were announced after North Atlantic Treaty Organisation reported a Russian naval buildup in the Mediterranean. The military said the drills would focus on anti-air and anti-submarine defence.
U.N. High Commissioner for Refugees Filippo Grandi said Friday that an offensive on Idlib is "going to be very hard".