Eurasec, established in 2000, is an international economic organization comprising Belarus, Kazakhstan, Kyrgyzstan, Russia, and Tajikistan. Three other former Soviet republics, Armenia, Moldova, and Ukraine have observer status.
"This is the sovereign right of any member state," the ministry said.
A Russian business daily said earlier on Wednesday that the reasons for the move were still unknown. However, the announcement came days after the EU lifted sanctions imposed on the republic in 2005, following the violent suppression of an uprising in the country that came to be known as the Andizhan massacre.
"Tashkent announced in mid-October that it was putting its membership on hold. They did not explain the reasons to us, but the Uzbek leadership has of late been often critical of Eurasec's performance, considering it an ineffective organization," Kommersant quoted an unidentified Russian Foreign Ministry official as saying.
He added that Uzbekistan was "extremely envious" of a customs union created by Russia, Kazakhstan and Belarus within the Eurasec framework.