Colombian officials are concerned that a dispute with the Swiss drugmaker Novartis over the patent and price of a groundbreaking cancer treatment could escalate and threaten U.S. funding for a pending peace deal that could end a half-century of war in the South American nation, according to leaked letters written by the Colombian Embassy.

In a letter last month to Colombia’s health minister, an official with the Colombian Embassy in Washington said that Senate Finance Committee staffer Everett Eissenstat had warned him that a plan to override the patent on Gleevec, the top-earning cancer drug for pharmaceutical giant Novartis last year, could damage Colombia’s reputation in the United States and interfere with U.S.-Colombian relations.

President Obama has made a $450 million commitment to aid implementation of the Colombian government’s peace deal between the government and the leftist guerrilla group Revolutionary Armed Forces of Columbia (FARC). A spokeswoman for the committee said that funding for the peace deal was not discussed in the meeting between Andrés Flórez and Eissenstat.

Colombian Health Minister Alejandro Gaviria said in an interview with the Associated Press on Tuesday that he would give Novartis a few weeks to lower the price on the leukemia drug Gleevec (known as Glivec outside the United States) before allowing it to be made by companies other than Novartis. The move, called compulsory licensing, breaks the monopolies of foreign drugmakers and allows competitors to sell cheaper generic versions in the country.

In one letter, obtained by the patient-advocacy group Knowledge Ecology International, Flórez, the embassy’s second-ranking official, wrote that the Senate staffer told him that even though Novartis is not an American company, the U.S. pharmaceutical industry was worried the case could become a “precedent.”

In a separate letter to the Colombian foreign minister April 27, Flórez wrote that the U.S. trade representative had requested a meeting to discuss the government’s patent plan.

A spokesman for the trade representative said that the requested meeting was held — after the release of an annual report that does not mention the patent issue in the section on Colombia — to discuss a broad array of issues related to intellectual property.

The Senate Finance Committee “has no jurisdiction over the Paz Colombia initiative and it was not discussed” at the meeting between Flórez and Eissenstat, the committee’s counsel for international trade, said Julia Lawless, a spokeswoman for its chairman, Sen. Orrin Hatch (R-Utah).

The letters provide a window into the behind-the-scenes tensions that arise when countries try to force down drug prices by overriding pharmaceutical patents. For years, nations struggling with limited health-care resources have been using compulsory licensing to give residents access to affordable versions of treatments.

Compulsory licenses can be used on any patent, not just drugs. The United States has used them to bypass patent holders for products such as night vision goggles and lead-free bullets, for example. Public Citizen, a patient advocacy group that tracks the use of compulsory licensing for pharmaceutical firms, found that since 1995, more than a dozen countries have exercised compulsory licenses on drugs, largely for HIV and cancer treatments. The reasons given range from public-health emergencies to anti-competitive practices to public interest.

It is difficult to measure how widely used compulsory licenses are in health care. Some African countries have granted licenses for entire classes of HIV drugs. Between 2006 and 2008, Thailand granted compulsory licenses for three HIV drugs, a blood-clot prevention drug and three cancer drugs. It initially sought a compulsory license for Gleevec, but ultimately canceled it because it came to an agreement with Novartis. In its most recent round of compulsory licenses in 2012, Indonesia issued licenses for seven HIV drugs and a hepatitis B medication. Ecuador has at least nine compulsory licenses for drugs.

The pharmaceutical industry defends its patents, which allow companies to make money after they have heavily invested in research and development of a drug. After patents expire, other companies are allowed to make cheaper generic versions.

In an emailed statement, Novartis said it was “actively seeking a resolution to discussions around our Glivec patent in Colombia that benefits patients, innovation and the healthcare system.”

Mark Grayson, a spokesman for the industry trade group PhRMA, said the organization could not comment about the situation in Colombia. Generally, he said, PhRMA believes that compulsory licenses should be used rarely, because if countries routinely bypass patents, it will undermine the incentive to do research and create new medicines.

The fights over these issues often create worries about international trade relations. Peter Maybarduk, director of the global access to medicines program at Public Citizen, spoke from Peru where he is currently working on a compulsory license for an HIV drug. He said that the Ministry of Health and the Ministry of Trade there are at odds because of concerns about the response of major businesses and trading partners.

“It’s a very ugly politics with a lot of lives at stake,” Maybarduk said. “When we give drug companies monopolies, then they’re going to charge whatever they can.”