Novaya Gazeta editor Dmitri Muratov said the document appears to have been prepared weeks before Ukraine's pro-Russian President Viktor Yanukovych was driven from office in February 2014, following weeks of anti-government protests in Kiev.
Muratov's disclosure came in an interview with Moscow's Ekho Moskvy radio.
He did not reveal how the document was obtained, but said he is confident it is authentic.
Muratov quotes the 2014 document as saying Moscow was obliged to intervene in Ukraine to protect against the possible loss of the Ukrainian market for Russia's natural gas.
He said the document also noted the risks to the Russian economy and to western European consumers, if Moscow were to lose control of pipelines carrying natural gas through Ukraine to Western markets.
The editor also said evidence shows the strategy document was prepared between February 4 and February 15, 2014.
Yanukovych did not abandon the presidency and flee to Russia until February 22.
Novaya Gazeta, founded by former Soviet leader Mikhail Gorbachev, is renowned for its aggressive investigations of corruption within the Kremlin, and has been nominated for a 2015 Nobel Peace Prize.
Six of its journalists have been killed since 2001, including Kremlin critic Anna Politskovskaya, who was shot dead at point blank range in 2006 after publishing reports critical of the Kremlin for Russian military actions in Chechnya.
Casualties reported Sunday
In other developments, two people were killed Sunday in a bomb explosion in the Ukrainian-held city of Kharkiv, as government supporters there and elsewhere marked the one-year anniversary of the overthrow of former president Yanukovych.
Authorities said at least 10 others were wounded.
Police said several suspects were arrested in this latest attack, with a Ukraine security aide saying they had received weapons and training in Russia.
In Kiev, several thousand people, led by President Petro Poroshenko, held a peaceful ceremony in Independence Square to mark the anniversary and to commemorate the deaths a year ago of 100 anti-Yanukovych protesters.
On Saturday, Ukraine and the rebels carried out a prisoner exchange, the first major sign of progress for an otherwise shaky truce signed more than a week ago.
The swap, involving 139 Ukrainian troops and 52 rebels, took place near the eastern village of Zholobok.
Since the ouster of the Yanukovych government, Russia annexed Ukraine's Crimean peninsula and separatists launched a rebellion in Ukraine's Russian-speaking east.
At least 5,700 people have been killed since fighting erupted 10 months ago.
Moscow has been widely accused of supplying rebels with arms, fighters and other supplies.
Moscow has repeatedly denied direct involvement.
Source: Voice of America