Speaking to reporters after his talks with his Ukrainian counterpart Anatoliy Gritsenko, Ivanov said Ukraine's possible entry into NATO may have a number of consequences, including Russia's decision to stop bilateral military-technical cooperation.
"This may happen. I suppose so," Ivanov was quoted by the Itar-Tass news agency as saying.
The Russian defense chief stressed that was only "one of the consequences" of Ukraine's possible accession to NATO and that other consequences include border issues.
Ukrainian President Viktor Yushchenko has made NATO membership a top goal of his country but the military bloc has shunned questions about when it might offer membership to this nation.
The accession to a military organization is a sovereign right of each country but any state also has a right to choose military-technical cooperation partners, Ivanov said.
During Gritsenko's visit to Moscow, he and Ivanov signed a military cooperation plan for 2006 and a cooperation agreement on providing flight safety for governmental aircraft.