More than 1,000 people have died in Mexico this year alone as the nation's drug cartels battle each other for lucrative drug routes into the US.

On Monday, Mexican authorities said it would offer a $2m reward for information leading to the arrest of each of its 24 top alleged drug lords, in its latest challenge to the cartels.

US-Mexico talks

Janet Napolitano, the homeland security secretary due to visit Mexico next week along with Eric Holder, the US attorney general, for a conference on arms-trafficking, said that the administration was still studying the idea of sending extra National Guard reserve troops to boost border security.

Speaking on Tuesday, Napolitano said she was confident that Mexico's government "will not fail" in its war against the cartels.

However, she dismissed suggestions that a border wall could stop drugs flowing into the US from Mexico, saying it "is not the best way" to prevent drugs from moving
across the border.

Investigators say nine out of 10 guns retrieved from crime scenes in Mexico are traced back to US gun dealers and US politicians have grown increasingly concerned over the prospect of violence spilling into US cities.

An increase in drug-related kidnappings has already been noted in some US cities, US authorities say.

In addition to Napolitano and Holder's visits, Hillary Clinton, the US secretary of state, is due to visit Mexico on Wednesday, while Barack Obama, the US president, is to hold talks with Felipe Calderon, his Mexican counterpart, on April 16 and 17.

Calderon declared tough action against the country's drugs gangs shortly after entering office in 2006, sending thousands of troops to the volatile border regions, a move which sparked an explosion of violence from the drugs cartels.