Andrés Manuel López Obrador

Andrés Manuel López Obrador, President of Mexico
President Donald Trump on Tuesday said that the United States is willing to help Mexico "wage WAR on the drug cartels" in the country, following the deaths of at least nine Americans, including six children, who reportedly came under attack in a highway ambush in a Mexican border state Monday.

"If Mexico needs or requests help in cleaning out these monsters, the United States stands ready, willing & able to get involved and do the job quickly and effectively," Trump wrote on Twitter. "The great new President of Mexico has made this a big issue, but the cartels have become so large and powerful that you sometimes need an army to defeat an army!"

"This is the time for Mexico, with the help of the United States, to wage WAR on the drug cartels and wipe them off the face of the earth. We merely await a call from your great new president!" Trump added.

Later Tuesday, the White House said that Trump offered "assistance" to Mexico in a conversation with the country's president, Manuel Lopez Obrador.

"President Trump made clear that the United States condemns these senseless acts of violence that took the lives of nine American citizens" in the call, and offered help to "ensure the perpetrators face justice," the White House said in a statement.

"The two leaders also discussed ongoing border cooperation and the strong bilateral ties between the United States and Mexico," the White House added.

Lopez Obrador said he thanked Trump for his willingness to help, adding that the Mexican government would ensure justice was done, Reuters reported.

The White House did not respond to CNBC's question about whether Trump's tweet suggested he was willing to send U.S. troops to Mexico to confront drug cartels.

Mexican Security Minister Alfonso Durazo said that the U.S. citizens ambushed on a Sonora highway late Monday may have been confused with criminal groups fighting for control in that region.

Comment: The Mormons themselves doubt that:
Julián LeBaron, leader of the Mormon community in northeastern Chihuahua, immediately rejected the government's first absurd theory of what happened: a case of mistaken identity. "They did not confuse them with anyone else," he said in an interview. "They brutally killed women and children."

Lopez Obrador has said he wants to crack down on drug-related violence in his country. But there was no immediate indication that Mexico would allow U.S. troops into the country to help with those efforts.

Asked Tuesday morning if Mexico would accept U.S. help on this security issue, Lopez Obrador said that he doesn't believe his country will need foreign intervention to deal with such cases, Reuters reported.

Lopez Obrador did say that Mexico is willing to work with the FBI, provided its national sovereignty is upheld, according to Reuters.