A former commander of Nato in Europe has called for the alliance to send arms and military advisers to Ukraine to help it fight Moscow-backed separatists.

James Stavridis said during a visit to London: “I think we should provide significant military assistance to the Ukrainian military. I don’t think we should limit ourselves to, non-lethal aid. I think we should provide ammunition, fuel, logistics. I think cyber-assistance would be very significant and helpful, as well as advice and potentially advisers.

“I don’t think there needs to be huge numbers of Nato troops on the ground. The Ukrainian military can resist what’s happening, but they need some assistance in order to do that.”

Ukraine announced on Friday that it would conscript 40,000 more soldiers next year and double its military budget, in an attempt to counter the separatist threat in the east.

The US and European states have offered only non-lethal assistance, despite Kiev’s appeals for weapons to help it reassert control over areas in eastern Ukraine currently under the sway of pro-Russia separatists. However, on Thursday the US Senate passed a bill authorising Barack Obama to provide military training and arms including anti-tank and anti-armour weapons.

Bob Corker, the senior Republican member of the Senate foreign relations committee, said: “The hesitant US response to Russia’s continued invasion of Ukraine threatens to escalate this conflict even further. Unanimous support for our bill demonstrates a firm commitment to Ukrainian sovereignty and to making sure [Vladimir] Putin pays for his assault on freedom and security in Europe.”

This month Nato established trust funds to help finance assistance to Ukraine in reforming its armed forces, but that too was limited to non-lethal help.

Stavridis, a retired US Navy admiral who was Nato supreme allied commander in Europe from 2009 to 2013, and is now dean of the Fletcher School of Law and Diplomacy at Tufts University in the US, also expressed concern about Putin’s recent rhetoric emphasising Russia’s nuclear arsenal.

In August Putin told a group of young supporters that Russia was one of the world’s leading nuclear powers, adding: “Russia’s partners … should understand it’s best not to mess with us.”

Stavridis said: “I’m hard-pressed to recall any nation that possesses nuclear weapons, rattling those nuclear weapons. Even during the cold war I don’t recall Nikita Kruschev rattling nuclear weapons, even at the height of the 62 [Cuban missile] crisis, because words have power.”

In his newly published memoir, The Accidental Admiral, Stavridis writes that Putin’s annexation of Crimea “brings back every bitter taste of the cold war like a bad vodka hangover”. On Friday he said: “The fact that President Putin chooses to rattle his nuclear sword should not cause us to draw back from assisting the Ukraine.”

However, Stavridis said the west should seek some form of “modus vivendi” with Russia emphasising areas of common interest, such as the Arctic, Afghanistan, counter-narcotics, counter-terrorism and counter-piracy as well as imposing limits on Iran’s nuclear programme, rather than stumbling backwards into another cold war.