The defence ministry in Berlin could send "up to six air force planes for air policing operations to the Baltic" region, the news magazine said in its online edition.
Germany also stands ready to provide a navy vessel.
A decision will be announced during a NATO meeting in Brussels on the Ukraine crisis on Tuesday, Der Spiegel added.
A foreign ministry official contacted by AFP said Germany would "take part, if necessary, in stepped-up routine operations within the alliance perimeter".
Estonia, Latvia and Lithuania have been rattled by Moscow's territorial ambitions in Ukraine after the ouster of the country's pro-Russian president Viktor Yanukovych last month.
The three Baltic states which joined NATO in 2004 on Saturday marked the 10th anniversary of their membership.
In Vilnius two US fighter jets roared across sunny skies as Lithuanian President Dalia Grybauskaite hailed NATO membership as "vitally important" to Baltic security.
The three countries of 6.3 million people were under Moscow's thumb before the collapse of the Soviet Union in 1991.
US Vice President Joe Biden said earlier this month Washington could dispatch forces to the region to reassure the ex-Soviet NATO allies which are
nervous about Russia's takeover of Crimea.
Washington has already sent six extra F-15 fighter jets to step up NATO's air patrols over the Baltics, and Britain, Denmark and France have also offered aircraft.
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