Homeland Security Secretary John Kelly and Attorney General Jeff Sessions promised Thursday to prosecute parents who pay people-traffickers, known as "coyotes," to help their children illegally cross the border into the US from Mexico.

The government had already included this rule in a memorandum published in February by the Department of Homeland Security, but on Thursday Kelly and Sessions promised to implement it at a press conference in El Paso during their first joint visit to the southern border.

In his remarks to reporters, Kelly said that the US will continue with its focus to halt illegal immigration, including prosecuting anyone who pays traffickers to bring people into the country illegally, especially those who traffic in children.

The people who cross the US border illegally are not respecting our nation's laws, Kelly added, and the administration wants to expel those who violate US laws.

Kelly and Sessions, the two Cabinet members with the greatest authority in immigration matters, reiterated their proposal to ensure compliance with the executive orders signed by President Donald Trump to end illegal immigration and drug trafficking.

Responding to reporters' questions, Kelly said that it is "absolutely essential" to follow through with the idea of building a wall along the border with Mexico to reduce illegal immigration, despite the fact that detentions of migrants in the region have declined in recent months.

In March 2017, the Border Patrol detained 16,600 people, 30 percent fewer than in February and a 64 percent decline from March of last year.

Kelly said that the US needs to continue with the effort, but the real aim is to work with the countries of Central America, Mexico and Colombia to halt illegal immigration.

Kelly is a retired Army general who headed the US Southern Command from 2012-2016, during which time he acquired a thorough knowledge of issues involving US partners in this hemisphere.

During their visit to the border, Sessions and Kelly met with a number of law enforcement agents, including personnel with the El Paso division of the Drug Enforcement Administration.

While the two officials were keeping to their agenda, a group of demonstrators marched in El Paso against the policies of the Trump administration carrying signs and wearing t-shirts bearing pro-immigrant and pro-refugee messages.