The US and Cuba will on Wednesday announce the opening of embassies in each other's capitals, a major step in re-establishing diplomatic ties severed in 1961, a senior US official has said.

Relations had been frozen since the early 1960s when the US broke links and imposed a trade embargo with the Communist island.

But the US and Cuba agreed to normalise relations at the end of 2014.

The country's two leaders held historic talks in April.

Since 1977, the US and Cuba have operated diplomatic missions called "interests sections" in each other's capitals under the legal protection of Switzerland. However, they do not enjoy the same status as full embassies.

Another milestone

US officials said President Barack Obama would make a formal announcement from the White House at 15:00 GMT on Wednesday.

It is still not clear exactly what the date will be for opening the embassies, but it is likely to be in mid-July, says the BBC's Cuba correspondent Will Grant.

The US State Department must give Congress two weeks' warning before the embassy can open, he adds.

It is the latest major milestone in a thawing process between the two countries' relations, which started with secret negotiations and was announced last December.