VIENTIANE, Laos — More than 40 years later, it is still a regular event in the countryside.

A child picks up what looks like a toy, a farmer hits a buried shell with a shovel, or a villager tries to snag some scrap metal — and an American bomb explodes.

Hundreds of people are killed or wounded each year by the remnants of the United States’ bombing campaign in Laos.

As Secretary of State John Kerry meets with Laotian leaders here Monday, unexploded bombs are expected to be a point of discussion with a developing country that will host a US president for the first time when President Obama visits later this year. The State Department declined to reveal what, if anything, Kerry will say publicly about the bombs during his visit.

Laos is the most bombed country in history, posing a poignant challenge for Kerry, who served in the Vietnam War, then returned home to become one of its leading protesters and launch his political career.

“We thought we were a moral country, yes, but we are now engaged in the most rampant bombing in the history of mankind,’’ Kerry said on “The Dick Cavett Show’’ in 1971, long before the scope of the so-called secret war in Laos was publicly known.

Kerry played a big role in normalizing relations with Vietnam as a US senator from Massachusetts. As America’s top diplomat, he now emphasizes bomb cleanup efforts as he builds ties in the region.

Honoring the 60th anniversary of diplomatic relations last year, Kerry said the United States continues to “make real our pledge to help clear Laos of unexploded ordnance.’’

The Obama administration and Congress have vastly increased funding for bomb cleanup and victim care. The $19.5 million in December’s yearlong spending bill is up from about $2 million per year less than a decade ago.

It will take far more to remedy a staggering problem. One-third of Laos — which is slightly larger than Minnesota — was bombed, and less than 1 percent of that land has been cleared of explosives.

US planes released cluster munitions full of about 270 million small “bombies’’ from 1964 to 1973, and an estimated 80 million of them did not explode. A mass of ball bearings and explosives smaller than a man’s fist, they unleash lethal amounts of shrapnel when triggered.

The United States is now helping fund Laos’s first national survey on unexploded bombs, as cleanup crews have long relied on old bombing maps and removal requests from villagers.

The survey aims to answer “how long is this going to take, and when are we going to finish this job,’’ said Channapha Khamvongsa, executive director of Washington-based advocacy group Legacies of War.

The prime reason for Kerry’s visit is to pave the way for a special meeting in California next month of the Association of Southeast Asian Nations. Later this year, at an ASEAN summit, Obama will become the first US president to visit Laos, continuing the administration’s “pivot’’ to Asia.

“China’s heavy footprint, especially in Laos’s north, has caused some friction with local people and officials, particularly over land issues,’’ said Murray Hiebert, a Southeast Asia expert at the Center for Strategic and International Studies. This “has provided Washington a strategic opportunity in Laos,’’ he said.

But Joshua Kurlantzick, a Southeast Asia expert at the Council on Foreign Relations, said America has only “modest’’ interests in the landlocked country of fewer than 7 million, and bomb cleanup money will not curry much favor.

“I’m sure they’re thankful, but at the same time, it’s mostly the US’s fault,’’ Kurlantzick said. “They’re not going to be that grateful.’’

The capital city of Vientiane sits on the Mekong River, which winds its way southward to its delta in Vietnam, where Kerry captained a swift boat during the war.

Those days informed his work in the Senate and State Department to remove explosives around the world.

“We looked for antipersonnel mines hidden in discarded C-rations, sometimes booby traps that were made from old artillery shells stuffed with explosives and wrapped in wax and bamboo, and on occasion we were hit by underwater mines, which were exploded remotely during the time when we would pass through,’’ Kerry said in 2014 when announcing a new report on global unexploded bomb and mine removal.

“So I learned something about the insidious nature of these instruments of battle.’’

Kerry earned a Silver Star, Bronze Star, and three purple hearts in the Navy in Vietnam, while the CIA and the Air Force were engaged in a secret air war in neighboring Laos.

US planes made 580,000 bombing runs over Laos in an attempt to disrupt Ho Chi Minh Trail supply lines and dislodge the Pathet Lao communists, dropping more bombs than the Allies dropped on Germany and Japan combined in World War II.

Such grim statistics and graphic documentary films greet visitors to the Cooperative Orthotic and Prosthetic Enterprise in Vientiane. The visitor center’s tower of prosthetic legs shows how COPE supports medical care for 1,000 survivors per year.

While about half of COPE’s funding comes from the US government, the organization’s Isabelle Bouan said a strong public statement from Kerry could inspire more private donors.

“We will see when he talks,’’ Bouan said. “Hopes are high.’’

Globe Correspondent Daniel Malloy can be reached at dpmalloy@gmail.com.