MEXICO CITY - US President Barack Obama and Mexican President Felipe Calderon pledged Thursday to work together to combat escalating drug violence along the border.

‘Both of our efforts have to be coordinated, both of our efforts have to be strengthened,’ Obama said during his first visit to Mexico since taking office, before he heads to the Summit of the Americas in Trinidad and Tobago.

Clashes between drug cartels and Mexican authorities have increased sharply in the last year as the Mexican government moves to crack down on narcotics with the strong financial and logistical backing of Washington.

The violence has prompted border security worries in the United States. One day before his visit, Obama named Alan Bersin as the border czar, a similar position he held under the Clinton administration.

The United States last month announced a huge expansion of its cooperation with Mexican police to help limit the illicit drug trade, including sending hundreds more US law enforcement officials and funds to the border under the Merida Initiative.

The Bush administration launched the initiative with Mexico and other countries in the region to support efforts to combat drug trafficking.

The White House also issued sanctions against three Mexican drug cartels, allowing the Treasury Department to seize and block financial assets of the Sinaloa Cartel, Los Zetas and La Familia Michoacana.

The death toll in Mexico’s drug war has topped 7,000 since January 2008. Obama praised Mexico for having ’so courageously taken on the drug cartels,’ and stressed his government’s commitment to stopping the flow of guns and cash that come into Mexico from the United States.

But Obama also conceded that more needed to be done in the United States to counter the drug violence by going after usage by American citizens and halting the flow of weapons from the United States to Mexico - a key complaint of the Mexican government.

‘It’s critical that we join together around issues that cannot be solved by any one nation,’ Obama said.

Obama and Calderon also discussed trade, climate change and the global financial crisis during the meeting. After staying overnight, Obama is to fly Friday to Trinidad and Tobago.

Obama’s visit to Mexico was met by more violence. Just hours before his arrival, 16 people were killed in the southern Mexican state of Guerrero in fighting between the military and suspected drug traffickers.