The legal process required to make Crimea part of Russia will be completed this week, Foreign Minister Sergei Lavrov said, two days after President Vladimir Putin signed a treaty to bring the Ukrainian region into Russia.
"Practical steps are being taken to implement the agreements on the entry of Crimea and (the Crimean port city of) Sevastopol into Russia," Itar-Tass news agency quoted Lavrov as saying.
"The legal process will be completed this week."
An unusually frank Nato Secretary General issued an unequivocal warning on the course of events should Russia attack Latvia or Estonia.
The West responds with sanctions and closer political ties with Ukraine as Russia's President seals the annexing of Crimea to much fanfare.
Supporters of the controversial fracking industry believe shale gas could be America's most potent weapon in the stand-off with Russia.