Colombian President Juan Manuel Santos expressed his gratitude Friday for the letter sent this week by his US counterpart, Donald Trump, in support of the efforts the South American country is making in the war on drugs.

"President Trump sent me a very positive, friendly letter of support. It was delivered yesterday. He confirms Colombia's help and the wish of the US to work together with us in the fight against drug trafficking, and thanks us for all we have done," Santos told a press conference.

In the letter, whose Spanish translation was provided by the Colombian president's office, Trump tells Santos that he trusts his efforts will help reduce the problem of coca crops and cocaine production in Colombia. He said they would work together on this important matter and make their already strong bilateral relationship even stronger.

The United States president reminded the Colombian head of state in the letter, dated Oct. 24, that he had previously expressed his concern about the vast expansion of coca crops and cocaine production in Colombia, as well as the possible consequences for the future if these activities are not curbed.

According to Trump, he was writing on this topic because he promised the American people that he would stop drugs from coming across the border and needed Santos's help to diminish drug production and trafficking in Colombia.

Last Oct. 23 the US Drug Enforcement Administration (DEA) reported that potential heroin production tripled between 2013-2016 in Mexico due in part to a reduction in the eradication of opium poppies, while the consumption of cocaine from Colombia increased significantly in the United States in recent years.

In 2016 the illegal coca crops in Colombia reached a record area of 188,000 hectares (464,000 acres), with a potential cocaine production of 710 metric tons, the White House said.