Drug-related violence in Mexico increasingly has the hallmarks of an insurgency, US Secretary of State Hillary Clinton has said.
The recent use of car bombs by drug cartels was one indication, she said, adding, "It's looking more and more like Colombia looked 20 years ago."
Her comments were made following a major speech to US foreign policy experts in Washington.
A Mexican government spokesman rejected Mrs Clinton's analogy.
Speaking in Mexico City, Alejandro Poire said the only aspect that the Mexican and Colombian conflicts share is their root cause - a high demand for drugs in the US.
Mr Poire also denied that the presence of drug cartels was tantamount to an insurgency, insisting that "all the efforts of the Mexican state were going into fighting criminals".
He added that "the collaboration with the US is an integral part of our strategy" in tackling drug cartels.
Mr Poire was responding to remarks Mrs Clinton made after a speech at the Council on Foreign Relations, a think tank.
Drug cartels, she said, "are showing more and more indices of insurgencies".
The traffickers were "in some cases, morphing into or making common cause with what we would consider an insurgency in Mexico and in Central America," she said.
The violence in Mexico was beginning to resemble Colombia of 20 years ago where insurgent groups at one time or another controlled some 40% of the country, Mrs Clinton added.
America's top diplomat said preventing the violence from spreading required improved institutional capacity, particularly in law enforcement, together with military support and the political will to fight the cartels.
"Mexico has capacity, and they're using that capacity, and they've been very willing to take advice, but the small countries in Central America do not have that capacity."
More than 28,000 people have died in drug-related violence in Mexico since President Felipe Calderon deployed the army to fight the cartels in 2006 and violence has spilled over into Central America.
The US has supported Mr Calderon's strategy, mainly through financial aid and military co-operation.
The Obama administration has also acknowledged some responsibility in the conflict, in part because of the flow of guns from the US to Mexican cartels.
But the BBC's Julian Miglierini in Mexico says Mrs Clinton's comments signal that concern in Washington about the situation in Mexico is even greater than what has been said in public so far.
As police and troops battle to contain the escalating violence, Mr Poire confirmed on Wednesday that police are holding seven people in connection with the massacre of 72 migrants last month.
The killings in the north-eastern state of Tamaulipas have been blamed on a powerful drug cartel.
During the speech in Washington, Mrs Clinton also said she declared "a new American moment" in global politics.
She said the model of American leadership "offers our best hope in a dangerous world".
The Obama administration has been criticised over a perceived lack of progress on its international goals.
Critics argue that Iran and North Korea maintain nuclear ambitions, the security situation in Afghanistan continues to be perilous and Israeli-Palestinian relations have yet to improve.
But Mrs Clinton said that the US had "begun to see the dividends of our strategy".
"We are advancing America's interests and making progress on some of our most pressing challenges," she said.
Mrs Clinton also said the world continued to look to the US for leadership in times of crisis, calling it both a responsibility and an unparalleled opportunity to seize upon.
"The world is counting on us. When old adversaries need an honest broker or fundamental freedoms need a champion, people turn to us," she said.
But she stressed the importance of international partnerships.
"This is no argument for America to go it alone," Mrs Clinton said.
"The world looks to us because America has the reach and resolve to mobilise the shared effort needed to solve problems on a global scale - in defence of our own interests, but also as a force for progress. In this we have no rival."