US President Donald Trump has said he will hold off on designating Mexican drug cartels as terrorist organisations for the present.

Mr Trump said in a tweet all preparations for the move had been completed and he was statutorily ready to issue a declaration.

But he said he had decided to delay at the request of Mexican President Andres Manuel Lopez Obrador.

The Mexican government has pushed back against Mr Trump’s plan, saying such a step by the US could lead to violations of its sovereignty.

“All necessary work has been completed to declare Mexican Cartels terrorist organizations,” Mr Trump wrote. “Statutorily we are ready to do so.”

“However, at the request of a man who I like and respect, and has worked so well with us, President Andres Manuel @LopezObrador— we will temporarily hold off on this designation.”

Mexico’s president thanked Mr Trump for his decision to “temporarily hold off” on designation Mexican drug cartels as terrorist organisations.

In a speech after Mr Trump’s tweet, López Obrador said: “I thank Trump for having put off the decision … and having chosen understanding and cooperation.”

Under pressure from Mr Trump’s threat to impose tariffs, Mexico has pressed thousands of national guard troops into service to help block Central American migrants from travelling through Mexico to reach the US.

In place of designating the cartels as terrorist outfits, Mr Trump said the US and Mexico would “step up our joint efforts to deal decisively with these vicious and every-growing organizations.”

Foreign Minister Marcelo Ebrard wrote that Mr López Obrador also “respects and appreciates” Mr Trump.

“Cooperation won, and there will be good results,” Mr Ebrard tweeted.

It was unclear if Mexico had promised Mr Trump anything in return for suspending the designation, which could have caused Mexico headaches.

Such a designation might require Mexico to periodically gain US certification that it was cooperating in fighting the cartels, and could potentially have affected Mexico’s access to international lending agencies.

Mexico President One Year Anniversary
Mexico’s President Andres Manuel Lopez Obrador has been pushing back against the terrorist categorisation (Marco Ugarte/AP)

The issue came to the fore after the November 4 slaughter of nine US-Mexico dual nationals in the northern border state of Sonora by drug cartel gunmen.

Mr Trump said in a radio interview last week he “absolutely” would move ahead with designating the drug cartels as terrorist organisations, attributing American deaths to drug trafficking and other activity by the cartels.

“I’ve been working on that for the last 90 days,” Mr Trump said in the interview when asked whether such a designation would be forthcoming.

Mr Trump was asked if he would designate the cartels “and start hitting them with drones and things like that?”

The President replied: “I don’t want to say what I’m going to do, but they will be designated.”