Bolton on Monday was photographed at a White House briefing holding a notepad with the scrawled line: "5,000 troops to Colombia."

"I haven't discussed that with Secretary Bolton," Shanahan said when asked if there was a plan to send thousands of troops to Colombia.

When repeatedly asked if he was ruling out such a deployment, Shanahan said: "I'm not commenting on it."

Bolton was holding a notepad while speaking to reporters about the crisis in Venezuela, where the US now recognizes opposition leader Juan Guaido as the country's interim president.

During his briefing, Bolton would not rule out the use of US troops in Venezuela.

"The president has made it clear on this matter that all options are on the table," he said.

The US military currently has about 200 troops in Colombia, and the two countries have developed close security ties over past decades.

Shanahan, who was previously deputy defense secretary, succeeded Jim Mattis at the start of the year after he quit amid disagreements with President Donald Trump.