President Donald Trump on Wednesday was mum on whether the United States would deploy 5,000 troops to Colombia to exert more pressure on Venezuela's leftist government but said he had many options for securing regime change.

"Our militaries are very focused and working together. And let's see how it all turns out," Trump told reporters during a meeting with Colombian counterpart Ivan Duque at the White House's Oval Office.

"We're going to make things turn out well. That's what we do. We make things work."

One of the reporters asked Trump about the controversial phrase "5,000 troops to Colombia" that could be read on a legal pad that National Security Adviser John Bolton carried into a press briefing on new Venezuela sanctions late last month.

"You'll see," Trump merely said, having earlier stated that he never talks about troop deployments. "There are a number of different solutions, a number of different options. And we look at all options."

Asked if he has a plan B if Venezuelan President Nicolas Maduro does not hand over power to the speaker of the opposition-controlled National Assembly, Juan Guaido, who in January proclaimed himself to be the country's legitimate head of state, Trump said he always has "plan B - and C, and D, and E, and F."

"I have great flexibility. I probably have more flexibility than any man that's ever been in this office."

The United States, Canada, Brazil, Argentina, Colombia, Germany, Spain, the United Kingdom and France are among the countries that say Maduro's May 2018 re-election victory was a sham and have recognized Guaido as the interim president of oil-rich Venezuela.

"A lot of things are happening in Venezuela that people don't know about. And there's a lot of support for what we're doing ... tremendous support," Trump said.

"I have great respect for the man that most people, many people, think is the real president," Trump said about Guaido, though without mentioning him by name.

"He's very brave ... I've seen what's happened in the streets and I've seen what's happened with executions, so I really give him a lot of credit. And I think it's going to work out very well."

Referring to a plan to deliver US humanitarian aid via Colombia to Venezuela, which has been racked by longstanding shortages of basic goods and hyperinflation, Trump said Maduro was "making a terrible mistake" in using his military to attempt to stop those supplies from entering.

Maduro says the US - which stepped up its pressure on Venezuela by imposing severe sanctions its oil industry late last month - is to blame for the country's economic woes and says the offer of humanitarian assistance is a pretext for a military invasion.

"They have to be able to let the food in. And in many cases it's getting in. They blocked one of the bridges, but they haven't been able to block the others. They'd like to try," Trump said.

Asked whether the US would be prepared to offer Maduro amnesty if he relinquishes power, Trump said that option had not been considered.

Duque, for his part, said Maduro's refusal to allow the entry of humanitarian aid constituted a "crime against humanity."

"I am very happy that the diplomatic blockade is working like no time before it, and I think the days for this dictatorship are about to end. We have to continue working in those lines," the Colombian president said.