Relations between Mexico and the United States are being pushed to breaking point amid accusations by Washington that Mexican officials have been “in bed for years” with drug traffickers, and reports of CIA agents freely operating south of the border.

“There are many who are betting on the defeat and failure of the Mexican government,” said Claudia Sheinbaum tersely on Wednesday, when asked about the allegations at a news conference. ”We want a good relationship with the United States government. What are our limits? The defence of sovereignty and respect for the Mexican people and their dignity.”

Sheinbaum’s comments follow inflammatory testimony from Drug Enforcement Agency (DEA) director Terry Cole before the US Senate on Tuesday.

“There’s no doubt that the narco traffickers and high-ranking government officials in Mexico have been in bed for years,” Cole said. “They are just as much responsible for the death and destruction of record amounts of Americans by cooperating, by conspiring, by helping, producing this poison to come across the border.”

Mexico has been under intense pressure from Washington for months to tackle drug trafficking groups, with President Donald Trump repeatedly threatening to send troops south of the border. But in recent weeks, that pressure has intensified, pushing Sheinbaum into a delicate balancing act between trying to appease her party and mollify an increasingly hawkish White House.

“It’s the most tense, the most difficult situation since at least the 1980s,” said former Mexican foreign minister Jorge Castañeda. “We’re in a moment the likes of which we have never seen, at least not in my memory.”

Despite Trump’s constant threats, Sheinbaum had kept a calm demeanor for months – denying that there would be any kind of US presence in Mexico even as she repeatedly bowed to Washington’s wishes. In the last year, the Mexican government has transferred nearly 100 cartel members to face justice in the US.

When Mexico, with the support of US intelligence, killed the leader of the country’s most powerful cartel in February, American officials celebrated, with deputy secretary of state Christopher Landau calling it a “great development”.

But relations began to fray last month when reports emerged that several CIA agents had been involved in a raid on a drug lab in northern Mexico, apparently without approval or prior knowledge from the federal government, potentially violating the country’s constitution.

Then, the US justice department charged the governor of Sinaloa, Rubén Rocha Moya, and nine other current and former Mexican officials for alleged ties to the Sinaloa cartel, accusing them of aiding in the massive importation of illicit drugs into the United States.

The indictment of a high-ranking member of Sheinbaum’s Morena party with almost no prior warning came as a slap in the face to the Mexican leader. Rather than handing him over, however, Sheinbaum closed ranks, arguing that Washington had failed to produce meaningful evidence.

“We will not allow any foreign government to come and decide the future of the Mexican people,” she said.

But last week, US acting attorney general Todd Blanche said there would be more charges against Mexican officials for links to cartels. The threat was made even more explicit on Tuesday when DEA director Cole said that Rocha’s indictment was “just the start about [sic] what’s to come in Mexico”.

Amid the flurry of collusion allegations, Sheinbaum is being increasingly backed into a corner, analysts say.

“Mexico has to be constantly on the defensive,” said Jesús Pérez Caballero, an expert on US-Mexico relations at the College of the Northern Border. “It’s very difficult for it to establish a counter-narrative that aligns with Mexico’s interests if it constantly has to respond to these accusations.”

Also on Tuesday, CNN published an explosive report alleging that the CIA had intensified covert operations in Mexico through the agency’s Ground Branch unit. According to CNN, the CIA “facilitated” the March assassination of a mid-level cartel member who was killed when a bomb exploded in his car, during the day, on one of the country’s busiest highways.

CNN also said that the CIA had been involved in multiple “deadly attacks” on cartel members since last year.

The report followed comments from Trump last week that a “land force” was already operating in Mexico.

“You’ll hear some complaints from … representatives from Mexico and other places,” Trump said. “But if they’re not going to do the job, then we’re going to do the job.”

Sheinbaum, however, was emphatic in her rejection of CNN’s reporting on Wednesday.

“It’s false that CIA agents operate in our territory,” she said during a news conference. “It’s a fiction about the size of the universe.”

Still, for all her bravura, it is likely that Sheinbaum will have to cave into America’s demands eventually: Mexico’s intimate relationship with the US, particularly on the economic front, leaves the Mexican leader with little wriggle room.

“She has a problem with the United States that is unsolvable,” said Castañeda. “She has to hand over Rocha, and the others they ask for. Period. There is no alternative. There is no possibility that she won’t do so without an enormous cost.”