Israel organized and paid for an influence campaign last year targeting U.S. lawmakers and the American public with pro-Israel messaging, as it aimed to foster support for its actions in the war with Gaza, according to officials involved in the effort and documents related to the operation.

The covert campaign was commissioned by Israel’s Ministry of Diaspora Affairs, a government body that connects Jews around the world with the State of Israel, four Israeli officials said. The ministry allocated about $2 million to the operation and hired Stoic, a political marketing firm in Tel Aviv, to carry it out, according to the officials and the documents.

The campaign began in October and remains active on the platform X. At its peak, it used hundreds of fake accounts that posed as real Americans on X, Facebook and Instagram to post pro-Israel comments. The accounts focused on U.S. lawmakers, particularly ones who are Black and Democrats, such as Representative Hakeem Jeffries, the House minority leader from New York, and Senator Raphael Warnock of Georgia, with posts urging them to continue funding Israel’s military.

ChatGPT, the artificial intelligence-powered chatbot, was used to generate many of the posts. The campaign also created three fake English-language news sites featuring pro-Israel articles.

The Israeli government’s connection to the influence operation, which The New York Times verified with four current and former members of the Ministry of Diaspora Affairs and documents about the campaign, has not previously been reported. FakeReporter, an Israeli misinformation watchdog, identified the effort in March. Last week, Meta, which owns Facebook and Instagram, and OpenAI, which makes ChatGPT, said they had also found and disrupted the operation.

The secretive campaign signals the lengths Israel was willing to go to sway American opinion on the war in Gaza. The United States has long been one of Israel’s staunchest allies, with President Biden recently signing a $15 billion military aid package for the country. But the conflict has been unpopular with many Americans, who have called for Mr. Biden to withdraw support for Israel in the face of mounting civilian deaths in Gaza.

The operation is the first documented case of the Israeli government’s organizing a campaign to influence the U.S. government, social media experts said. While coordinated government-backed campaigns are not uncommon, they are typically difficult to prove. Iran, North Korea, China, Russia and the United States are widely believed to back similar efforts around the world, but often mask their involvement by outsourcing the work to private companies or running them through a third country.

“Israel’s role in this is reckless and probably ineffective,” said Achiya Schatz, the executive director of FakeReporter. That Israel “ran an operation that interferes in U.S. politics is extremely irresponsible.”

Israel’s Ministry of Diaspora Affairs denied involvement in the campaign and said it had no connection to Stoic. Stoic didn’t respond to requests for comment.

The campaign didn’t have a widespread impact, Meta and OpenAI said last week. The fake accounts accumulated more than 40,000 followers across X, Facebook and Instagram, FakeReporter found. But many of those followers may have been bots and didn’t generate a large audience, Meta said.

The operation began just weeks into the war in October, according to Israeli officials and the documents on the effort. Dozens of Israeli tech start-ups received emails and WhatsApp messages that month inviting them to join urgent meetings to become “digital soldiers” for Israel during the war, according to messages viewed by The Times. Some of the emails and messages were sent from Israeli government officials, while others came from tech start-ups and incubators.

The first meeting was held in Tel Aviv in mid-October. It appeared to be an informal gathering where Israelis could volunteer their technical skills to help the country’s war effort, three attendees said. Members of several government ministries also took part, they said.

Participants were told that they could be “warriors for Israel” and that “digital campaigns” could be run on behalf of the country, according to recordings of the meetings.

The Ministry of Diaspora Affairs commissioned a campaign aimed at the United States, the Israeli officials said. A budget of about $2 million was set, according to one message viewed by The Times.

Stoic was hired to run the campaign. On its website and on LinkedIn, Stoic says it was founded in 2017 by a team of political and business strategists and calls itself a political marketing and business intelligence firm. Other companies may have been hired to run additional campaigns, one Israeli official said.

Many of the campaign’s fake accounts on X, Instagram and Facebook posed as fictional American students, concerned citizens and local constituents. The accounts shared articles and statistics that backed Israel’s position in the war.

The operation focused on more than a dozen members of Congress, many of whom are Black and Democrats, according to an analysis by FakeReporter. Representative Ritchie Torres, a Democrat from New York who is outspoken about his pro-Israel views, was targeted in addition to Mr. Jeffries and Mr. Warnock.

Some of the fake accounts responded to posts by Mr. Torres on X by commenting on antisemitism on college campuses and in major U.S. cities. In response to a Dec. 8 post on X by Mr. Torres about fire safety, one fake account replied, “Hamas is perpetrating the conflict,” referring to the Islamist militant group. The post included a hashtag that said Jews were being persecuted.

On Facebook, the fake accounts posted on Mr. Jeffries’s public page by asking if he had seen a report about the United Nations’ employing members of Hamas in Gaza.

Mr. Torres, Mr. Jeffries and Mr. Warnock didn’t respond to requests for comment.

The campaign also created three fake news sites with names like Non-Agenda and UnFold Magazine, which stole and rewrote material from outlets including CNN and The Wall Street Journal to promote Israel’s stance during the war, according to FakeReporter’s analysis. Fake accounts on Reddit then linked to the articles on the so-called news sites to help promote them.

The effort was sloppy. Profile pictures used in some accounts sometimes didn’t match the fictional personas they cultivated, and the language used in posts was stilted.

In at least two instances, accounts with profile photos of Black men posted about being a “middle-aged Jewish woman.” On 118 posts in which the fake accounts shared pro-Israel articles, the same sentence appeared: “I gotta reevaluate my opinions due to this new information.”

Last week, Meta and OpenAI published reports attributing the influence campaign to Stoic. Meta said it had removed 510 Facebook accounts, 11 Facebook pages, 32 Instagram accounts and one Facebook group tied to the operation. OpenAI said Stoic had created fictional personas and biographies meant to stand in for real people on social media services used in Israel, Canada and the United States to post anti-Islamic messages. Many of the posts remain on X.

X didn’t respond to a request for comment.

On its LinkedIn page, Stoic has promoted its ability to run campaigns backed by A.I. “As we look ahead, it’s clear that A.I.’s role in political campaigns is set for a transformative leap, reshaping the way campaigns are strategized, executed and evaluated,” it wrote.

By Friday, Stoic had removed those posts from LinkedIn.