Washington, Aug. 21 -- The Trump administration has intensified its economic pressure on Cuba by subjecting nine state-owned firms in the construction, mining, and metals sectors to new penalties, while simultaneously tightening the enforcement of American regulations that restrict US citizens travelling to the island from engaging in business with state-controlled enterprises.

The latest measures follow Havana's rejection of the curbs after several American citizens returning from events associated with Fidel Castro's 100th birthday were briefly detained at Miami airport, as the island continues to grapple with a deteriorating economic downturn.

According to the US Treasury and State departments, the newly announced restrictions also f...