The Skripals, father and daughter, were found unconscious on a park bench in Salisbury, and 12 days later they are still in critical condition at a hospital.
Britain blames the Kremlin for the brazen nerve agent attack.
On Thursday, the U.S., Germany, and France issued a rare joint statement condemning Russia for the attack, and on Friday, NATO and Australia said they stand with Britain, too.
Britain also signaled it might hit Russian President Vladimir Putin's loyal allies where it hurts: their luxury "Londongrad" real estate.
Wealthy Russians started moving money into Britain in the mid-1990s, using murky shell companies to invest tens of billions of dollars in multimillion-dollar London mansions and other assets, like soccer teams and newspapers, The New York Times reports.
Foreign Secretary Boris Johnson suggested Thursday that Britain might target Putin associates in a new anti-corruption drive. »