Arriving in Luxembourg for talks with EU foreign ministers, Mr Johnson said they would be considering further economic sanctions as well as looking to maintain the diplomatic pressure on Moscow.
But after talks in London on Sunday with US Secretary of State John Kerry and other allies made clear there was no appetite for Western military intervention in the conflict, he acknowledged the initiative lay with Mr Putin.
“We will be discussing how to keep the pressure up on the Assad regime and on its puppeteers in the form of the Russian government,” he told reporters.
“The future salvation of Aleppo lies really with Assad regime and above all with the Russians. It is up to them to pull the plug on this thing, to see sense, and I appeal to the greatness of the Russian people to choose a different path and to go for peace and get us back on the path of negotiations in Geneva.”