The European Union and Canada have warned of reprisals after the United States for the first time allowed lawsuits against foreign companies operating in Cuba, including EU and Canadian firms.

US Secretary of State Mike Pompeo announced on Wednesday that Washington will end routine wavers to the 1996 Helms-Burton act on May 2 and allow for lawsuits over property seized by Cuba. 

"The EU and Canada consider the extraterritorial application of unilateral Cuba-related measures contrary to international law," they said in a joint statement from Brussels.

It was signed by EU foreign policy chief Federica Mogherini and Trade Commissioner Cecilia Malmstrom, along with Canadian Foreign Minister Chrystia Freeland.

"We are determined to work together to protect the interests of our companies in the context of the WTO," they noted.

"Our respective laws allow any US claims to be followed by counter-claims in European and Canadian courts," the three officials said.

"The US decision to allow suits against foreign companies can only lead to an unnecessary spiral of legal actions," they warned.

US unveils new sanctions on Cuba, Venezuela

US National Security Adviser John Bolton announced a series of new sanctions against Cuba and Venezuela on Wednesday.

Mogherini and Malmstrom had previously sent a similar warning to Pompeo in a letter dated April 10, according to a copy of a letter obtained by AFP.

"Any person or company doing business in Cuba should heed this announcement," Pompeo told reporters in the US.

Under the Title II provision of the Helms-Burton Act, any companies that operate in property seized by Cuba during Fidel Castro�s 1959 communist revolution could face lawsuits in US courts from the vast and politically powerful Cuban American diaspora.