Vice President Harris will depart Sunday for Guatemala and Mexico, a two-day trip crafted to highlight the Biden administration’s efforts to remedy what it calls the “root causes” of mass migration from Central America to the United States.

Traveling abroad for her first time as vice president, Harris will arrive Sunday evening in Guatemala bearing gifts: pledges for hundreds of thousands of coronavirus vaccine doses, $310 million in regional humanitarian aid, and a $4 billion long-term plan to boost development and security across Central America. Those sweeteners may be used to offset what are expected to be tougher messages about battling corruption and upholding democratic norms.

In Mexico, where Harris will arrive Monday night, she will meet with President Andrés Manuel López Obrador to discuss expanding immigration enforcement cooperation with the United States as part of a regional approach to managing migration, administration officials say.

In advance of the trip, White House officials have sought to lower expectations that Harris’s efforts will produce short-term results at the U.S. southern border. Since President Biden took office, the number of migrants taken into custody by U.S. agents per month has rocketed to the highest levels in 20 years, with record numbers of teenagers and children crossing without parents.

 Mazin Alfaqih, a special adviser to Harris for Central America’s Northern Triangle region, which includes Guatemala, Honduras and El Salvador, said the Biden administration recognizes that “U.S. government and foreign assistance alone cannot tackle this problem.”

“There needs to be political will on the part of the government, but we also are looking to partner with multilateral organizations, the private sector and other entities to really build a comprehensive approach that addresses the many root causes of migration in the region,” said Alfaqih, speaking to reporters in advance of the trip.

In March, Biden directed Harris to address the underlying causes of migration — including poverty, violence, climate change and government corruption. It marked the first major issue in her portfolio, which this month expanded to include spearheading the administration’s efforts to counteract Republican efforts to enact voting restrictions — assignments that place her in the middle of a pitched partisan battle being fought at multiple levels of government.

On immigration, the administration has emphasized that Harris’s role would be diplomatic, not managerial, and similar to the one played by Biden when he was Barack Obama’s vice president. Harris has relatively little foreign policy experience, though the administration has said she tackled some immigration issues as the California attorney general and senator from that border state.

Administration officials, from the president down, have said she is not responsible for dealing with the more politically fraught elements of U.S. border enforcement. More than 16,000 teenagers and children remain in U.S. government shelters, down from more than 21,000 in March, when the Biden administration was caught off-guard and overcrowding inside border tents reached crisis levels.

More unaccompanied minors have arrived from Guatemala than any other nation, U.S. Customs and Border Protection data show.

Republicans, including several with presidential ambitions, have rushed to connect Harris to the surge at the border. Some have taken to calling her Biden’s “border czar.”

The GOP pile-on is an effort to link Harris to a policy that has confounded presidents of both parties for decades and threatens to overshadow Biden’s handling of other major issues ­— and to dent Harris’s political future. Harris is widely seen as a presidential aspirant and a potential heir to Biden, particularly if the 78-year-old decides not to seek reelection in 2024. Her efforts over the next week will be closely watched and will help inform the narrative of Harris as a potential world leader.

Andrew Selee, president of the Migration Policy Institute, a nonpartisan think tank whose proposals are influential with the administration, said the expected result of Harris’s engagement in Central America “can’t be a sudden drop in migration.”

“I think she needs to keep expectations low, and show she’s listening to people in Guatemala,” Selee said. “The more this is framed in terms of managing migration, instead of stopping it, and helping people in Central America achieve their aspirations for development, rather than bringing development to them, will keep expectations realistic.”

Harris has been briefed over the past two months by experts on policies that affect migrant flows, and she has conducted virtual bilateral meetings with the presidents of Guatemala and Mexico. The early shape of the strategy also involves spurring private investment, and last month a dozen companies and organizations announced commitments to support inclusive economic development in the Northern Triangle, including Chobani, Duolingo, the Harvard T.H. Chan School of Public Health and Microsoft.

Harris will meet with Mexico’s López Obrador and Guatemalan President Alejandro Giammattei during her trip, and she is also scheduled to meet with U.S. Embassy officials and aid workers.

Officials at the State Department and the U.S. Agency for International Development have in recent months reconsidered the successes and failures of previous efforts to deter migration through development, particularly the Alliance for Prosperity, launched during the Obama administration.

“There are lessons to be learned from the last four or five years and the way USAID has done a lot of their programs,” Mileydi Guilarte, deputy assistant administrator for USAID’s Bureau for Latin America and the Caribbean, said in an interview. “And that’s really what we’re doing right now — to take stock of what has worked and what hasn’t.”

U.S. officials say the next round of development funding for the Northern Triangle countries, which Harris will discuss on her visit, should include more consultation with communities from which people are migrating, and a focus on creating urban economic hubs that will encourage internal — instead of external — migration.

But within the Biden administration, there is ambivalence about whether development funding is an effective tool to reduce migration in the short or even medium term. Some officials have suggested that the best solution would be a dramatic expansion of U.S. work visa programs, and they see the increase of 6,000 H-2B nonimmigrant visas for citizens of Honduras, Guatemala and El Salvador as insufficient.

As Northern Triangle countries struggle to procure coronavirus vaccine, some governments have alluded to the prospect of the United States stepping in to fill the void as part of a broader migration-deterrence package. Giammattei told reporters that Harris pledged to deliver 500,000 doses to Guatemala. Mexico said it will receive an additional 1 million.

Leaders in Honduras and Guatemala have been broadly receptive of the Biden administration’s plan to reduce migration through development assistance, even as the United States has suggested that its strategy would include a renewed anti-corruption drive.

“The last four years, the U.S. has not cared about corruption in these countries, and there’s been full counterattack,” said one senior administration official, speaking on the condition of anonymity because they were not authorized to discuss Harris’s trip. Efforts to promote good governance have lost ground to “groups making the calculus that the U.S. will care more about migration and combating the drug trade than corruption, and they’re testing that theory,” the official said. “Our theory is that we can do both.”

Last month, in response to attacks on the Salvadoran judiciary and “larger concerns about transparency and accountability,” USAID redirected millions of dollars in aid away from the Salvadoran government. The funds instead will be allocated to civil society organizations in the country.

The episode touched on a central tension in the Biden administration’s aid effort: U.S. officials believe that the program’s effectiveness will require the buy-in of local governments. But in many cases, the United States doesn’t trust its partners enough to make those investments.

Salvadoran President Nayib Bukele responded swiftly to the U.S. decision, saying he would not support the civil society groups.

“It’s good they receive foreign financing, because they will not receive a cent from the Salvadoran people,” Bukele wrote on Twitter.

Eric Olson, a veteran Central America analyst who is director of the Central America-D.C. Platform at the Seattle International Foundation, said Harris will have to balance the need to work with the region’s leaders while not allowing that engagement to be manipulated for domestic advantage when anti-corruption efforts and democratic rule are weakening.

“I think the U.S. needs to continue to talk to these governments while at the same time making very clear what the boundaries are and what the U.S. is willing to do,” Olson said. “That’s the big challenge for her — to not be manipulated and misused to project the idea that you’re endorsing everything the government is doing.”

Sieff reported from Matamoros, Mexico.