"This is a red line and should be (seen as such) by all countries in the region, especially Iraq's neighbours," he said in an interview with CNN Turk television. Syria, like Iraq and Turkey, has a Kurdish minority.
Al-Asad was answering a question about Syria's stance towards the creation of any form of Kurdish entity in Iraq - an issue US authorities say is up to Iraqis alone.
"Any division of Iraq will not affect Iraq or Turkey alone as some do believe. This would have an impact on all (of Iraq's) neighbours," said Al-Asad, who starts a state visit to Turkey on Tuesday, the first there by a Syrian head of state.
Analysts say Turkey and Syria share the concern that the creation of a Kurdish state in northern Iraq could ignite secessionist aspirations among their Kurdish minorities.
Syria has traditionally sought to blend its minorities, both ethnic and religious, under a national unity umbrella. The official position of Syrian Kurdish groupings is not to pursue sectarian goals, but to safeguard their cultural identity.
"Any division of Iraq will not affect Iraq or Turkey alone as some do believe. This would have an impact on all (of Iraq's) neighbours"
"If Iraq is not united, the occupation will not end and without Iraq's unity, there will not be stability for Iraq or our countries," Al-Asad said.
Kurds at loggerheads
Iraqi Kurds are at loggerheads with US occupation authorities over a future autonomous Kurdish state in the north of the country.
A source close to the Kurdish bloc in Iraq's Governing Council told Aljazeera.net on Monday the US administrator in Iraq, Paul Bremer, was stalling over Kurdish federalism proposals.
According to the source, Bremer asked Jalal Talabani, leader of the Patriotic Union of Kurdistan (PUK) and Massud Barzani, leader of the Kurdistan Democratic Party (KDP), to be patient in calling for Iraqi federalism.
The US governor wants the "situation" in Iraq to return to normal and a constitution to be agreed upon before Kurdish autonomy is considered.
"We have accepted federalism in principle, but there are different forms of federalism in the world and I cannot tell you for the moment what the final form will be in Iraq"
Iraq's Governing Council
But the source said: "Bremer's position didn’t satisfy the ambition of the two Kurdish leaders who think that opportunities will be narrowed as time goes by.
Kurdish media reaction
"Bremer was talking about a new federal democratic Iraq without stating the form of federalism and whether it was the same federalism the Kurds have proposed.
"Kurdish media in Arbil considered Bremer's announcements an
evasion from an answer awaited by Kurds."
The current president of the 25-member council, Adnan Pachachi, has also urged the Kurds to be patient.
He said: "We have accepted federalism in principle, but there are different forms of federalism in the world and I cannot tell you for the moment what the final form will be in Iraq."
Kurdish parties want to divide Iraq into two regions - one Kurdish and one Arab.