WASHINGTON — Richard G. Olson, a retired diplomat who recently served as ambassador to Pakistan and the United Arab Emirates, said he would plead guilty to charges of illegally lobbying for the government of Qatar and failure to disclose gifts he received while he was an ambassador, according to court documents.

Mr. Olson, who worked as a Foreign Service officer for 34 years, was U.S. special representative for Afghanistan and Pakistan from 2015 until 2016, when he retired. In that role, he reported directly to Secretary of State John Kerry. From 2012 to 2015, he was the ambassador to Pakistan. His first tour as an ambassador was in the United Arab Emirates, from 2008 to 2011.

The Justice Department said in a filing that Mr. Olson had avoided disclosing in required ethics documents that he had received a first-class airplane ticket from New Mexico to London valued at more than $18,000 and a stay in a luxury hotel in London in January 2015.

The payments were made by a Pakistani American businessman whose name was not revealed in the documents. In London, the ambassador met with a businessman from Bahrain, who soon offered him a one-year contract with a salary of $300,000 that would start after he left the State Department.

The U.S. government bars senior officials from doing lobbying work on behalf of foreign entities during a “cooling off” period of one year after they leave the government. Mr. Olson violated this when he went to work for the Pakistani American businessman in December 2016 and began receiving monthly payments of $20,000. The businessman’s company did lobbying for the government of Qatar.

The details of the case against Mr. Olson were reported earlier on Wednesday by Axios. The court documents were filed with a federal court in the Central District of California in early April. The two charges brought by the Justice Department are misdemeanors. Mr. Olson was not charged with violating the Foreign Agents Registration Act.

Mr. Olson’s lawyer, Michael Hannon, did not provide comment for this article.

Mr. Olson lobbied on behalf of Qatar in Washington on two issues, the Justice Department said in the filings. The first involved efforts to persuade American officials to establish a U.S. Customs and Border Protection preclearance facility in the main airport in Doha, Qatar. Having such a facility gives a host country and its national airlines significant advantages in operating flights to the United States — the airlines can fly directly to more than 160 destinations in the United States even if the U.S. airport has no customs clearance facilities.

Prosecutors indicated in a court filing that the Pakistani American businessman’s company was being paid by a company associated with a Qatari official to get Washington to set up such a facility in Doha. According to the filing, the businessman drew up a contract in October 2016 that said a holding company controlled by a Qatari government official would pay the businessman’s company $3.5 million per year plus a 20 percent “success fee.”

The filing noted that the United Arab Emirates, a rival to Qatar and where Mr. Olson had served as ambassador, had a preclearance facility. In April 2013, the State Department signed a treaty with the Emirates that established the facility at Abu Dhabi International Airport.

The other lobbying effort in which Mr. Olson was involved occurred after Saudi Arabia, the Emirates, Bahrain and Egypt cut diplomatic ties with Qatar in 2017 and blocked flights and ships from Qatar from using their airspace and sea lanes. The rupture became an international crisis. American military officials had to scramble to deal with the consequences of the blockade because the U.S. military’s main air base in the Middle East is in Qatar.

Rex Tillerson, the first secretary of state under President Donald J. Trump, told U.S. lawmakers in 2019, a year after he had been forced out, that he had been taken by surprise by the diplomatic crisis. He said Jared Kushner, Mr. Trump’s son-in-law and a White House adviser, had spoken secretly with Saudi and Emirati leaders about their plans to impose the blockade during a visit to Riyadh in 2017.

Mr. Olson was paid to lobby officials in the Trump administration to encourage the U.S. government to help get the blockade lifted and repair diplomatic relations among the Persian Gulf nations, the Justice Department prosecutors said in their filing.

Qatar and the Emirates have poured money into Washington-based companies and research groups in recent years to try to influence U.S. policy. Thomas J. Barrack Jr., a friend of Mr. Trump, was arrested in July 2021 on charges of illegally lobbying for the Emirates. Elliott Broidy, a Trump ally and former Republican official, also lobbied on behalf of the Emirates, and he was charged in 2020 with illegally lobbying for a Malaysian financier.

Mr. Olson received multiple awards during his more than three decades in the Foreign Service, according to an official online biography. He retired as a career minister, the second-highest rank in the service.

Mr. Olson was also posted in Mexico, Uganda, Tunisia, Saudi Arabia, Ethiopia and Iraq.

When Mr. Olson retired in November 2016, Mr. Kerry said in a statement, “Rick is quite simply one of our most distinguished diplomats, a career member of the Senior Foreign Service who has been on the forefront of our work in the Middle East, Africa and most recently in Afghanistan and Pakistan.”