Jeremy Hunt will challenge the EU to stand "shoulder-to-shoulder" with the US and Britain over Russian aggression, as he makes his first visit to Washington as Foreign Secretary.
Mr Hunt will use a speech on Tuesday to urge the bloc's members to ensure the allies speak with "one voice" against transgressions by Moscow "whenever and wherever they occur, from the streets of Salisbury to the fate of Crimea".
EU nations including Germany and France were among dozens of countries that expelled Russian diplomats following March's Novichok nerve agent attack on former double agent Sergei Skripal and his daughter Yulia, which also resulted in the death of a British woman, Dawn Sturgess, in June.
But some have since reached out to President Putin's regime, with French president Emmanuel Macron travelling to St Petersburg to call on Russia to work "hand-in-hand" with Europe, and Italy questioning whether sanctions imposed over the 2014 annexation of Crimea should continue.
His visit also follows the historic and controversial summit between Vladimir Putin and Donald Trump in Helsinki, which led to widespread criticism of the US president.
In a speech at the US Institute of Peace, Mr Hunt is due to say that under Mr Putin Russia's "aggressive and malign behaviour undermines the international order that keeps us safe".
He will say: "Of course we must engage with Moscow, but we must also be blunt: Russia's foreign policy under President Putin has made the world a more dangerous place.
"And today, the United Kingdom asks its allies to go further by calling on the European Union to ensure its sanctions against Russia are comprehensive, and that we truly stand shoulder to shoulder with the US.
"That means calling out and responding to transgressions with one voice whenever and wherever they occur, from the streets of Salisbury to the fate of Crimea."
German chancellor Angela Merkel became the latest leader to engage with Mr Putin, holding talks with him on Saturday - after he had first stopped in Austria to attend the wedding of the country's foreign minister Karin Kneissl.
Mr Hunt will also discuss Brexit in his speech, which looks at the raft of challenges to the "international rules-based system that has kept us safe for decades".
He will warn that a "catastrophic" no-deal Brexit represents "one of the biggest threats to European unity".