Raul Castro's criticism of Trump was part of a televised speech he delivered Sunday evening local time in Caracas. The Cuban leader had traveled to the Venezuelan capital to attend a summit meeting of leftist political leaders from Latin and South American nations commemorating the fourth anniversary of Venezuelan ex-President Hugo Chavez's death.

Castro took particular aim at Trump's agenda on trade and immigration.

"The new agenda of the US government threatens to unleash an extreme and egotistical trade policy that will impact the competitiveness of our foreign trade; violate environmental agreements ... hunt down and deport migrants," the Cuban president said.

Castro also called Trump's proposed border wall with Mexico "irrational" and argued its construction targeted not just Mexicans but all Latin Americans.

"You can't contain poverty, catastrophes and migrants with walls, but with cooperation, understanding and peace," Castro said, simultaneously describing growing inequality due to an unjust global economic system as the root cause of migration.

On January 25, Trump issued an executive order calling for "the immediate construction of a physical wall" along the US-Mexican border. His administration is expected to invite prototype bids for the wall as early as Monday.

An erosion of a detente?

Castro's vocal criticism of Trump policy signals an icy wind entering what had recently been increasingly warm - if still delicate - relations between the socialist island nation and its large northern neighbor.

In February, the Trump White House said it was undertaking "a full review of all US policies towards Cuba."

The same month Trump also met with Republican Senator from Florida and Cuba hardliner Marco Rubio, later stating he and the senator shared similar perspectives on Cuba.

The meeting echoed Trump's pre-inaugural warning that once ensconced in the Oval Office, he would backtrack from the normalized relations achieved during the last years of the Obama administration unless a "better deal" could be achieved.

Castro's critique, in combination with Trump's Cuba policy indications, opens the possibility of a return to strict isolationist policies and escalated tension.

In a reversal of more than 50 years of isolationism, the Obama administration pursued a policy of detente including the relaxation of travel restrictions to the island, the removal of Cuba from the US state terrorism list, and the promise to work toward closer economic cooperation.  In December 2014, Obama and Castro announced the renewal of diplomatic ties, and in March 2016 Obama became the first US president in office to visit the island in about 90 years.