Guatemalan President Bernardo Arevalo was welcomed on Monday at the White House, where he won pledges of strong bilateral ties and backing for his anti-corruption campaign.

Arevalo held talks with Vice President Kamala Harris to discuss the "root" causes of immigration -- a thorny election-year issue for the Democratic White House -- and then later met with President Joe Biden.

Biden said on X, formerly Twitter, that his previously unannounced meeting with Arevalo was to "congratulate him in person on his inauguration, and to reiterate our commitment to a strong partnership between the United States and Guatemala."

A former lawmaker, diplomat and sociologist, Arevalo pulled off a major upset when he swept from obscurity to win elections last August, firing up voters weary of graft in one of Latin America's poorest nations.

But his anti-corruption crusade put him in the crosshairs of prosecutors accused of graft themselves and closely aligned with the country's entrenched political and economic ruling class.

They tried to overturn the election results with a series of legal actions that Arevalo has repeatedly denounced as a "coup" attempt, and even a last-ditch effort that saw his inauguration delayed by several hours.

"Your election has brought a sense of optimism to the people of America and around the world," Harris told Arevalo before their meeting.

"As you hold corrupt actors accountable and promote good governance, we support you," she said.

Arevalo called the meeting with Harris a "historic moment" that reflects "what we believe will be continued strong support from the United States."

He added that his government was committed to doing everything to meet the "great expectations" for Guatemala held by the United States and the international community.

As a show of support, Harris announced a battery of measures for Guatemala, including $170 million in aid, expansion of a support program for thousands of young people at risk of emigration, technical assistance for reforms, and promotion of trade in textiles.

Nearly 130,000 Guatemalans illegally crossed the US-Mexico border from October to February, among a total of 1,150,000 migrants intercepted during that period, according to the US Border Patrol.

Biden in his meeting thanked Arevalo for hosting a regional summit on migration scheduled for next month, the White House said.