"If there is no breakthrough and real unity does not begin, this situation (break-up) will become reality," Lavrov was quoted as saying by the ITAR-TASS news agency.
The comment came amid soul-searching by the main countries involved in Iraq -- notably the United States and Britain -- and by the Iraqi government itself over prospects for keeping the country united.
Since the US-led invasion in 2003, Iraq has become involved in a series of internal conflicts which threaten to tear it apart. In addition to the insurgency against military occupation there is vicious civil unrest, much of it pitting different ethnic and religious groups against one another.
Calls for a de facto partition have come from within Iraq, including one on Tuesday from the largest Shiite Muslim political grouping.
Abdel Aziz al-Hakim, leader of the Supreme Council for the Islamic Revolution in Iraq (SCIRI), told supporters that a federal system with only loose central control would prevent the return of dictatorship.
"Federalism will guarantee that the injustice of the past will not revisit our children nor our grandchildren," Hakim said in a speech for the Eid al-Fitr holidays marking the end of the Muslim holy month of Ramazan.
Iraq's post-Saddam constitution, passed by referendum in October 2005, describes the country as a "democratic, federal, representative republic" but a decision on what kind of federal system to use has yet to be taken.
The supreme leader of neighbouring Iran, meanwhile, called on Iraqis to remain united in the face of what he called US plots to destabilise the region.
Addressing thousands of devotees massed into the grounds of a huge mosque in Tehran to mark the Eid al-Fitr festival, Ayatollah Ali Khamenei said Muslims in the Middle East had to be on their guard against "the cunning United States policies".

Copyright AFP (Agence France-Presse), 2006