SAN FRANCISCO (AP) — President Joe Biden and Mexican President Andrés Manuel López Obrador pledged Friday to work side-by-side to confront illicit fentanyl trafficking into the U.S. and to manage the growing number of migrants traveling north to the border between their nation.

"Nothing is beyond our reach in my view if Mexico and the United States stand together and work together," Biden said.

Biden's relationship with López Obrador has at times been tense, in part because of Biden's willingness to criticize Mexico on topics such as fentanyl production and the killing of journalists. And López Obrador isn't afraid to snub the U.S. leader. He skipped a Los Angeles summit last year where leaders tackled the issue of migration because the U.S. didn't invite Cuba, Nicaragua or Venezuela. He also initially said he would skip this year's APEC conference, but changed his mind.

The two men were all smiles and compliments before the press on Friday, with Biden telling López Obrador: "I couldn't have a better partner than you," and the Mexican leader calling Biden a "good man" and an "extraordinary president."

They were in San Francisco for the annual Asia-Pacific Economic Cooperation conference, where Biden has held a series of face-to-face meetings with other leaders, including China's President Xi Jinping and the leaders of Japan and South Korea, as he seeks to reassure the region that the U.S. and China are competitors, not zero-sum rivals.

Biden and Lopez Obrador set to work talking migration as the U.S. strains to manage a rising number of southern border crossings.

They also discussed deadly fentanyl trafficking, particularly after Biden secured an agreement with Xi to curb the illicit opioid. Mexico and China are the primary sources for synthetic fentanyl trafficked into the U.S. Nearly all the chemicals needed to make it come from China, and the drugs are then mass-produced in Mexico and trafficked via cartels into the U.S.

"I want to tell you about my great conversation with Xi Jinping on that issue," Biden told López Obrador.

The issues of fentanyl and immigration are related. Human smuggling over the border is a part of cartel operations that also include drug trafficking into the U.S.

"We're working side-by-side to combat organized crime," Biden said.

The powerful opioid is the deadliest drug in the U.S. today. More than 100,000 deaths a year have been linked to drug overdoses since 2020 and about two-thirds of those are related to fentanyl. The annual death toll is more than 10 times the level in 1988, at the height of the crack epidemic.

"We're aware of the damage it poses to the United states youth," López Obrador said through an interpreter.

And migration challenges facing the U.S. are growing increasingly intractable. Democratic leaders at the state and local level are begging for federal assistance to help care for migrant families living in squalid shelters and sleeping in police stations. Republicans are loudly critical of Biden's border policies as too lax. And Congress has not passed an immigration overhaul in decades.

Biden asked for $14 billion from Congress for border security but the temporary spending bill he just signed did not have funding for the border, Ukraine aid or Israel.

There are rising numbers of migrants at the border. Arrests for illegal crossings along the U.S.-Mexico line were up 21% to 218,763 in September, and Biden has repeatedly said Congress should act to fix outdated immigration laws. But in the meantime, his administration has developed policies that aim to deter migrants from making a dangerous and often deadly journey while also opening up new legal immigration pathways.

Mexico's support is critical to any push by the U.S. to clamp down at the southern border, particularly as migrants from nations as far away as Haiti are making the trek on foot up through Mexico and are not easily sent back to their home countries.

López Obrador said the administration's policies of cracking down on illegal crossings while opening up other legal pathways for others to come to the U.S. lawfully was "a humane way to address the migration phenomenon."

Earlier this year, Mexico agreed to continue to accept migrants from Venezuela, Haiti, Cuba and Nicaragua who are turned away at the border, and up to 100,000 people from Honduras, Guatemala and El Salvador who have family in the U.S. will be eligible to live and work there.

According to data on asylum-seekers in Mexico, people from Haiti remained at the top with 18,860 so far this year, higher than the total for the whole of 2022.

Meanwhile, the U.S. is accepting 30,000 people per month from the four countries for two years and offering them the ability to work, as long as they come legally, have eligible sponsors and pass vetting and background checks.

Guatemala and Colombia will open regional hubs where people can go to make asylum claims in the hope of stopping them from traveling on foot. But Mexico has so far refused to allow the U.S. to set one up.

López Obrador also used Friday's meeting with Biden to take up the case for Cuba and urged the U.S. president to resume a dialogue with the island nation and end U.S. sanctions.

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Associated Press writer Christopher Sherman in Mexico City contributed to this report.