CK Hutchison said Thursday it wants more than $1.5 billion from Panama.

The Hong Kong company said Panama broke an investment protection treaty.

It called the port seizure a "state attack campaign" on its things.

Panama's government took the Balboa and Cristobal ports in February.

The ports are at the two ends of the Panama Canal.

Panama's Supreme Court said the agreement of CK Hutchison's subsidiary was not legal.

The ports became a big problem in U.S.-China tensions after Donald Trump came back to the White House.

He said China was "running" the canal.

Panama owns and runs the canal, but CK Hutchison's subsidiary had run the two ports since 1997.

The family of Hong Kong's richest man, Li Ka-shing, controls CK Hutchison.

Last year, it said it would sell its world port business for $23 billion.

A group led by BlackRock would buy it.

That deal has not moved much because of world tensions.

In March, the subsidiary asked for at least $2 billion from Panama about the takeover.

CK Hutchison said Thursday's new case is about its treaty rights.

Those rights are different from the subsidiary's contract rights.

In April, the subsidiary also started a legal case against Maersk about port work in Panama.

Maersk said it did not think it was at fault.