US Secretary of State Mike Pompeo said there was a "substantial chance" that the suspected poisoning of Kremlin critic Alexei Navalny was ordered by senior Russian officials.
"There is a substantial chance that this actually came from senior Russian officials," Pompeo told the Ben Shapiro radio programme, according to a transcript released by the State Department.
Pompeo said the United States was evaluating how it would respond.
"We'll make sure we do our part to do whatever we can to reduce the risk that things like this happen again," he said.
Navalny, who is being treated in a Berlin hospital, was airlifted to Germany after falling ill on a Russian domestic flight last month.
Germany says he was poisoned with a Soviet-style Novichok nerve agent in an attempt to murder him. Russia has said it has seen no evidence that Navalny was poisoned.
"I think the world has matured and come to an understanding that this is not how normal countries operate, and this will prove costly for the Russians," Pompeo said.
The Group of Seven (G7) foreign ministers issued a statement on Tuesday condemning the "confirmed poisoning" of Navalny.
Israel bombarded northern Gaza overnight in some of the heaviest shelling in weeks, causing panic amongst residents and flattening neighbourhoods in an area from which the Israeli army had previously down its troops, residents said on Tuesday.
Russia launched a drone attack on Ukraine that injured seven people in the Black Sea port of Odesa, two of them children, and also targeted Kyiv, the capital, Ukraine's military officials said early on Tuesday.
A Delhi court on Tuesday extended the pre-trial detention of Indian opposition leader Arvind Kejriwal until May 7 in a corruption case, the legal news website Live Law reported.
Taiwan's quake-hit eastern county of Hualien was rattled by more than 200 aftershocks late on Monday and early on Tuesday, but only minor damage was reported and no casualties and major chipmaker TSMC said it saw no impact on operations.
Two Malaysian navy helicopters collided in mid-air during a rehearsal for a naval parade on Tuesday, killing all 10 crew members aboard, the navy said in a statement.