BUENOS AIRES — Iran and Hezbollah, the Lebanese militia it supports, were the central focus of a Latin America counterterrorism conference Friday that Secretary of State Mike Pompeo said was part of a “concerted effort to reengage with our partners in the hemisphere.”

In an opening statement to the gathering of 18 nations in Argentina’s capital, Pompeo said that international terrorist groups such as al-Qaeda and the Islamic State “continue to seek a lasting presence in our hemisphere.”

“The roots of these terror groups may be many miles away, but their branches twist around the globe — raising funds, seeking recruits, probing for our weaknesses, challenging our defenses,” Pompeo said.

But “Iran-backed Hezbollah,” he said, is a particular threat in South America, where it has long maintained active fundraising and recruiting efforts in the tri-border area of Argentina, Paraguay and Brazil, and in Venezuela.

The administration’s increased interest in South America, after largely ignoring the region in its first year, coincides with several strands of President Trump’s foreign policy. In addition to Hezbollah’s activities, efforts to replace the Venezuelan government of Nicolás Maduro, regional trade competition with China and the election of a spate of more conservative South American governments have drawn attention from Washington.

Pompeo’s trip, which also includes stops in Ecuador, Mexico and El Salvador, is his sixth to the region, including attendance at the Group of 20 summit in Argentina last November and an April trip that included Chile, Paraguay and Colombia. A year ago, he also traveled to Mexico.

Pompeo’s visit to Argentina coincided with the 25th anniversary of the worst terrorist assault in this city, a July 18, 1994, car bomb attack on the main Jewish community center, which left 85 dead and more than 300 wounded.

At a commemoration at the rebuilt site Friday morning, Pompeo lit a candle under a plaque with the names of the dead. “They were killed by members of a terrorist group, Hezbollah, and had help that day from Iran,” which he said provided “logistical support and funding through its Islamic Revolutionary Guard Corps.”

Ariel Eichbaum, president of the Israel-Argentine Mutual Association, also charged Hezbollah with responsibility, as has the Argentine government. But Eichbaum, while calling for the killers to be brought to justice, centered his remarks on Argentina’s immigrant population, including Jews. Noting that they had gathered to form a community, he said that “we can show the world how to live together.”

Pompeo, at a later news conference with Argentine Foreign Minister Jorge Faurie, praised President Mauricio Macri, whose government on Thursday designated Hezbollah a terrorist organization — a first in South America — and said its assets would be frozen.

Brazil and Paraguay did not follow suit, despite U.S. entreaties. But Faurie announced that they, along with the United States, had decided to form a “regional mechanism” to combat “illicit activities . . . as well as possible linkages to transnational crime and the financing of terrorism.”

Pompeo met privately with Macri at the presidential residence in the suburbs of Buenos Aires. The State Department said Pompeo “reaffirmed U.S. support for Argentina’s economic reform agenda.”

Macri faces a tough reelection battle in October against the resurgent Peronist party, as his efforts to right the country’s faltering economy have found little traction. The United States has expanded Argentina’s access to the Overseas Private Investment Corporation, but has not responded to the country’s call to lessen heavy tariffs on imports of Argentine biodiesel fuel.

At his news conference, Pompeo was asked about U.S. claims that it shot down an Iranian drone this week, and Iranian Foreign Minister Mohammad Javad Zarif’s denial that the incident happened.

“It went down, and that fact that . . . Zarif either didn’t know or lied about it, I can’t account for. It happened,” Pompeo said.

Zarif made his remarks during a visit to the United Nations in New York. “I would welcome the chance to get access to the Iranian media in the same way he gets access to the American media,” Pompeo said. “I think that would be fantastic.”

Correction: An earlier version of this story misstated the number of times Secretary of State Mike Pompeo has visited Latin America. He has made six trips to the region.