US President Donald Trump welcomed his Colombian counterpart, Juan Manuel Santos, to the White House, officials said.

This was Trump's first meeting with the South American leader following his government's hard-won peace deal with the the Revolutionary Armed Forces of Colombia, (FARC), reports NBC News.

Trump called the effort to end the 52-year conflict that left more than 220,000 dead and displaced more than five million a "long process" and a "great thing to watch".

"That's not easy after so many years of war," Trump said during a joint press conference with Santos after their meeting at the Oval Office on Thursday, adding there's "nothing tougher than peace and we want to make peace all over the world".

Trump also reaffirmed the US' "willingness to assist Colombia's strategy to target and eliminate drug trafficking networks, illicit financings, coca (plant used to make cocaine) cultivation and cocaine production," Efe news reported.

Illicit cultivation of coca in Colombia grew by 18 per cent in 2016 to a record 188,000 hectares (about 470,000 acres) planted, from which an estimated 710 tonnes of cocaine could be produced, according to White House figures.

Santos, in response, said that Colombia was working to reduce coca production and combat drug trafficking networks.

The Colombian leader sought on his visit to the White House to emphasize the bilateral relations between the two nations and convince Trump that US support for Colombia during its post-conflict phase is in Washington's strategic interests.

Just a few weeks ago, Congress approved the funds former President Barack Obama had requested for the new post-conflict phase of US assistance to Bogota, including about $450 million in both diplomatic and defense aid.

Trump, however, has expressed his intention to cut the State Department budget by 26 per cent, which could result in a smaller US contribution to Colombia in the coming fiscal year.

The meeting with the Colombian President comes just one day before Trump's first foreign trip, where he will travel to Saudi Arabia, Israel, and the Vatican before attending the G7 and NATO summit in Taormina and Brussels, respectively.