"We have to do everything possible to prepare this set of documents before the Minsk summit," Vladimir Shkolnik said at a meeting in the Central Asian country's largest city Almaty, adding that the remaining 16 documents were still being coordinated.
The CES is designed to ensure free movement of goods, services, capital, and people between its member states, and ultimately to abolish tariffs and harmonize markets in the key areas such as transportation and energy.
The organization, agreed on in principle in early 2003 by Russia, Ukraine, Belarus, and Kazakhstan, the four largest CIS nations, would be open for other countries to join, and could eventually lead to a single currency.
"If we fail to find an acceptable solution before June 22 for each of the three parties - while Ukraine is following its own path and its position is now unclear - then these issues will all the same be raised to an intergovernmental level," he said.
