Colombian President Juan Manuel Santos has said Cuba will not attend a summit of Americas nations in Colombia next month, following talks with Cuban President Raul Castro in Havana.

The issue of Cuba's possible attendance had threatened to overshadow April's Cartagena summit, with the US insisting that Cuba should not attend, while a Venezuela-led bloc of leftist states said they would boycott the event if Havana was not represented.

The Americas summit usually involves nations who are members of the Organisation of American States (OAS), from which Cuba was suspended in 1962 because of its communist system.

The OAS voted to lift the ban on Cuban membership in 2009, but Cuba has not rejoined because it says the organisation is heavily influenced by Washington.

But Santos, making the first visit to the island by a Colombian leader in a decade, said Cuba's agreement not to attend had averted a diplomatic showdown.

Santos, who will chair the summit, thanked Castro for saying that he did not want to "create a problem" for Colombia.

"Colombia wants the situation of Cuba and its participation to be discussed in a constructive manner at the Cartagena Summit," said Santos, whose country is considered Washington's strongest ally in the region.

Ecuadorian President Rafael Correa had proposed that members of the left-leaning ALBA block of Latin American and Caribbean nations, which also includes Bolivia and Nicaragua, boycott the conference in protest if Cuba was formally excluded.