The British Army's ability to respond to threats "will be eroded if we don't keep up with our adversaries", reads the speech, approved by Defense Secretary Gavin Williamson, that comes amid speculation of potential defense cuts, according to the BBC.
The warning comes after Russia conducted large scale military exercises last year, including simulated attacks across northern Europe, from Kaliningrad to Lithuania, the BBC reports.
In the speech, which will take place at the Royal United Services Institute on Monday, Gen Sir Nick Carter will highlight Russia's new cyber warfare capabilities.
Gen Carter will also highlight the Russian army's long-range missile strike capability. While Russian forces were intervening in Syria, 26 missiles were deployed from a 1,500km (930 mile) range.
He will add that Russia is building an increasingly aggressive expeditionary force, which already boasts capabilities the British Army would struggle to match.
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Last year Prime Minister Theresa May said Russia had "mounted a sustained campaign of cyber espionage
This intervention from Gen Carter is as much an appeal for more money to fund the armed forces and to avoid further cuts.
There are concerns in the armed forces that the review will prioritize counter-cyber attacks and terrorism, rather than major defense.
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Mr Williamson said "hard work" is taking place to give the armed forces the "right resources".
Some MPs have called to increase defense spending to 3% of GDP, the BBC wrote.