It said the president would sign the treaty with Crimea's leader.
Putin signed an order on Monday "to approve the draft treaty between the Russian Federation and the Republic of Crimea on adopting the Republic of Crimea into the Russian Federation," Reuters reported.
The order is part of a series of steps to bring Crimea into Russia after voters there approved the move in a weekend referendum that Ukraine and the West have called denounced by Ukraine and the West as illegal.
It comes the day after Putin ignored the toughest sanctions against Moscow since the end of the Cold War, Russian President Vladimir Putin has recognised Ukraine's Crimean Peninsula as an "independent and sovereign country".
The brief decree posted on the Kremlin's website on Monday came just hours after the United States and the European Union announced asset freezes and other sanctions against Russian and Ukrainian officials involved in the Crimean crisis.
Tensions between Russia and the West have soared since Russian troops took effective control of Crimea, a strategic Black Sea peninsula last month and supported the Sunday referendum that overwhelmingly called for annexation by Russia.
Putin took a step closer to formally annexing the majority ethnic-Russian region by recognising its independence from Ukraine, opening the way for Russian lawmakers to later endorse its accession.
The US placed sanctions on seven Russian officials, including deputy Prime Minister Dmitry Rogozin, and four Ukrainians accused of usurping Ukraine's territorial integrity, including ousted President Viktor Yanukovich.