Donald Trump has warned US action against suspected Venezuelan drug traffickers will move to the land "very soon".

American forces have carried out at least 21 strikes on boats it claims were carrying narcotics to its shores over the last few months.

The US has accused the South American country's president, Nicolas Maduro, of being involved in the drugs trade - a claim he denies.

Venezuela has said the attacks, which have killed more than 80 people, amount to murder.

'We warned them,' says Trump

America's most advanced aircraft carrier is among the ships that have been deployed to the Caribbean Sea and eastern Pacific as part of Operation Southern Spear.

Mr Trump said on Thursday he was preparing to significantly ramp up the response.

"You probably noticed that people aren't wanting to be delivering by sea, and we'll be starting to stop them by land also," he told military service members in a call.

"The land is easier, but that's going to start very soon."

"We warned them to stop sending poison to our country," Mr Trump added.

The US has released videos of boats being targeted, but hasn't provided evidence - such as photos of their cargo - to support the smuggling claims.

Even if the boats are cartel vessels, Sky's chief correspondent Stuart Ramsay says the final destination for the drugs is likely to be Europe and West Africa.

The Pentagon has sought to justify the strikes by labelling the drug gangs as foreign terrorist organisations - putting them on par with the likes of al Qaeda and Hamas.

This week it formally designated Cartel de los Soles (Cartel of the Suns) as such, and said the group was headed by Mr Maduro and "other high-ranking individuals" from his regime.

Another Venezuelan drugs group, Tren de Aragua, was designated a terror organisation by the US in January.

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Mr Maduro - seen by most countries as a dictator who's cheated elections - has accused the US of "fabricating" a war to overthrow him and install a more favourable government.

Venezuelan officials have also claimed Mr Trump's true motivation is access to the country's plentiful oil reserves and other natural resources such as gold and diamonds.

Experts say Mr Maduro, 63, could use oil as a bargaining chip in any future negotiations.

Mr Trump has said previously he would be open to talks - but that prospect seems unlikely, with the Venezuelan leader wielding a sword this week as he vowed to "defend every inch of this blessed land from imperialist threat".