Sanctions targeting Russia's multi-billion pound diamond industry and crucial metals will be unveiled by Rishi Sunak.
Marking the first day of the G7 summit of world leaders in Hiroshima, the PM will announce an import ban on the gems in an attempt to hit Vladimir Putin's war chest.
Members of the G7, including the United States, Japan, France, and Germany are also expected to reveal further sanctions during the summit.
Downing Street said legislation banning diamond imports - also hitting imports of Russian-origin copper, aluminium, and nickel - will be introduced later this year.
The Foreign Office will also produce a sanction list on Friday of 86 people and companies "from Putin's military industrial complex, and those involved in key revenue streams such as energy, metal, and shipping", No10 said.
"We're expecting a fairly similar approach [from other countries]," the Prime Minister's spokesperson told reporters flying to Hiroshima.
"We're always trying to move in lockstep".
It comes as world leaders prepare to visit the Hiroshima Peace Park - the site of the atomic bomb dome - before holding talks on Russia's brutal war in Ukraine.
Mr Sunak said: "For the sake of global peace and security, we must show that brutal violence and coercion does not reap rewards.
"As today's announcements demonstrate, the G7 remains unified in the face of the threat from Russia and steadfast in our support of Ukraine.
He added: "We are meeting today in Hiroshima, a city that exemplifies both the horrors of war and the dividends of peace."
"We must redouble our efforts to defend the values of freedom, democracy and tolerance, both in Ukraine and here in the Indo-Pacific".
* Follow Mirror Politics on Snapchat, Tiktok, Twitter and Facebook.
