THIS is the moment Mexican cartel gangsters opened fire on US Border Patrol along the southern border.

Footage shows the thugs firing on drones watching them as they creep closer to crossing into the United States.

The salvo comes as Donald Trump has declared the deadly groups as terrorists and the boss of one cartel is preparing his gang to fight American forces.

The latest shootout on the border erupted at about 2pm local time on Monday near Guadalupe Guerra, Texas.

Video showed four gangsters with high-powered rifles shooting at the Texan drone following them.

Chris Olivarez, spokesperson with the Texas Department of Public Safety, released the footage of cartel members crossing from Mexico onto an island in the Rio Grande River.

The thugs try to hide in the scrub and bushes as the craft hovers ahead filming them.

Olivarez claimed the four were escaping military forces and were seeking “refuge” on an island between the US and Mexico.

They appeared to remain in Mexico and did not cross officially into the US.

Olivarez said: “The State of Texas will continue to monitor the area closely & use every resource available to prevent transnational threats to our law enforcement partners & the homeland.”

Nearby Fronton Island is known as “cartel island” and was cleared of scrub by Texan officials to try and deter human trafficking and cartel gangsters from using the island to cross.

It comes as the leader of one of the most dangerous and successful cartels is said to be “preparing” the cartel to face Trump.

Nemesio Oseguera Cervantes, known as ‘El Mencho’, leads the Jalisco Nueva Generación Cartel (CJNG) and has called an emergency meeting of his top commanders.

The gangsters are now buying high-caliber weapons according to journalist and podcaster Anabel Hernández as they prepare to face down the US military.

Hernández said: “After Trump announced his war against the Mexican cartels, it [CJNG] is the organisation that is preparing itself the fastest with powerful weapons to fight.

“Although the leader of the CJNG claims to have arrangements with the Government of Mexico, he does not rule out that there may be covert operations by the Trump administration.”

Hernández claimed that the CJNG is now monitoring Mexican airports, cities, and even US consulates in the country.

The cartel appears to be worried that US military special forces could be deployed in Mexico as Trump tries to crush the gangs.

There is also a $15 million (£12 million) bounty on the head of El Mencho and legal proceedings open against him in Washington DC.

The Pentagon has sent 1,500 active service troops to the border who will fly helicopters to assist Border Patrol and help build barriers.

The US military also will provide aircraft for Department of Homeland Security deportation flights for more than 5,000 detained migrants.

In one of his first actions as US president, Trump designated the murderous gangs from Mexico, Colombia, Venezuela and El Salvador as foreign terrorist organisations – and promised swift results at any cost.

Trump may even launch airstrikes in Mexico as he seeks to destroy the groups that pose a threat to his “Fortress America”.