US President Joe Biden and his Mexican counterpart Andres Manuel Lopez Obrador said Monday they had ordered concrete steps to reduce illegal border crossings, an explosive issue in November's US election.

But a joint statement issued by the two leaders after they spoke on Sunday gave no details of the measures to curb crossings over the southern US border with Mexico.

Republicans, led by Biden's election rival Donald Trump, have sought to make border security a key issue ahead of the vote, portraying Biden as soft on stopping illegal immigration.

"The two leaders ordered their national security teams to work together to immediately implement concrete measures to significantly reduce irregular border crossings while protecting human rights," said the joint statement released by the White House.

At a news conference in Mexico, Lopez Obrador said Biden initiated the call and that he wanted the two countries to work together as "neighbors, friends and trading partners."

The Mexican leader also said migrant flows across the border are down thanks to social programs his government is carrying out in the region.

Biden has previously said he is considering so-called executive action to tackle the problem, including toughening asylum procedures and even temporarily closing the border.

But he has faced a backlash from within his party over steps considered too tough on asylum seekers.

Polls show most voters blame Biden for the unprecedented number of migrants crossing the border, which rose to a record high of 10,000 a day in December but has fallen in recent months.

More than 2.4 million migrants crossed the southern US border in 2023 alone, largely from Central America and Venezuela as they flee poverty, violence, and disasters exacerbated by climate change.

Trump has ramped up his anti-immigration rhetoric as he seeks an extraordinary White House comeback, repeatedly speaking of migrants "poisoning the blood" of the United States.

The US and Mexican leaders meanwhile also "pledged to advance initiatives to address the root causes of migration throughout the Western Hemisphere," including measures aimed at economic and security progress, the statement said.

Lopez Obrador has previously touted his cooperation with Biden to tighten measures on the Mexican side of the border to stop the flow of migrants.

But he has also urged Washington to spend billions each year to alleviate poverty in Latin America, ease sanctions on the far-left governments in Venezuela and Cuba, and grant legal status to millions of Mexicans living in the United States.