WASHINGTON — U.S. food aid is taking months to reach needy nations despite an urgent global food crisis, a bipartisan group of senators said Tuesday, urging the Biden administration to accelerate delivery as the war in Ukraine pushes more countries closer to famine.

In a letter to U.S. Agency for International Development Administrator Samantha Power, one Democrat and 12 Republican lawmakers said that inadequate stewardship of funding and staffing shortages jeopardized the effectiveness of U.S. efforts against mounting global hunger.

“Unless the United States translates well-meaning rhetoric and appropriated dollars into a swift humanitarian response, Russia’s crimes against humanity and weaponization of the global food supply will go unpunished,” the senators wrote. “The most significant proposal of humanitarian aid in modern U.S. history must be accompanied by an infrastructure that assumes more prudent risk and quickly delivers support.”

In the letter, a copy of which was obtained by The Washington Post, the lawmakers asked for “an explanation of why such lifesaving aid may take half a year to deliver.”

The request comes as the United Nations’ World Food Program warns about what it is calling a global emergency, saying the number of people who are acutely food insecure has nearly tripled since 2019 to some 345 million. The agency, which provides food relief, requires some $22 billion to meet emergency needs in 2022 but faces a major funding gap given soaring prices of basic commodities.

Experts say the war in Ukraine, normally a major grain exporter, has worsened a slow-building crisis created by a combination of global conflict, climate change, the coronavirus pandemic and increasing concentration in the worldwide food production and distribution system.

The United States and its allies, seeking to help Ukraine repel Russia’s invasion, have promised strong support for food insecurity, but advocates say more is needed. Countries in the Middle East and Africa, among those who typically rely on imports from Ukraine, are among the worst affected.

The agency, in reply to the letter, described the U.S. response to the food crisis as unmatched “in speed and scale,” and said that by the end of fiscal year on Sept. 30, USAID will have spent more than 60 percent of the $7 billion in supplemental funding for humanitarian aid.

“This assistance has been critical to mounting not just a robust response to meet the needs of Ukrainians, but also rapidly scaling up assistance to places already experiencing acute food insecurity and hit hard by Russia’s war in Ukraine like Somalia, Ethiopia, Kenya, and Yemen,” a USAID spokesperson said in a statement, speaking on the condition of anonymity due to rules established by the agency.

USAID said the remainder of supplemental funding would be spent by the end of 2022 “to ensure we are able to maintain a steady infusion of resources into humanitarian programs through the fall and winter when we expect to see the worst effects of the food crisis in many parts of the world.”

But the senators allege that USAID is moving too slowly and is failing to get approved funding out the door, meaning that aid approved in a March assistance package for Ukraine may not reach recipients until the fall. They said the agency has a woefully inadequate system for overseeing food aid contracts, with a staff of fewer than five contracting officers to manage more than 1,200 contracts.

The lawmakers, led by Sen. Joni Ernst, R-Iowa, also cited reports that USAID leaders were “responsible for the relatively slow rate of programming by second guessing humanitarian priorities and seeking to deviate funding to support irrelevant development priorities, thereby undermining humanitarian requirements to scale-up and respond quickly to save lives and alleviate human suffering.”

The letter’s signatories also included Sen. James Inhofe, R-Okla., and Sen. James Risch, R-Idaho, the top Republicans on the Senate Armed Services Committee and the Senate Foreign Relations Committee, respectively.

Ernst, along with Sen. Chris Coons, D-Del., is spearheading a separate effort to waive requirements that half of U.S. food aid under certain authorities be transported on U.S.-flagged vessels, which can make aid delivery slower and more costly.