Although the president halted virtually all other refugee admissions shortly after he took office in January, his administration hastily put together a program to allow in white South Africans, who he claims have been the victims of racial persecution in their home country.

The administration plans to send government officials to Washington Dulles International Airport in Virginia for an event marking the arrival of the South Africans, who belong to the white minority Afrikaner ethnic group, according to the memo from the Department of Health and Human Services. The administration initially planned to welcome the Afrikaners on Monday, but some officials familiar with the matter cautioned that the plans remained in flux, subject to flight logistics and processing of the group.

The arrival of the Afrikaners would cement Mr. Trump’s efforts to upend a program that for decades has allowed thousands of people fleeing war, famine and natural disaster to find safe haven in the United States.

The Afrikaners, however, had to wait no more than three months.

The arrival of the white South Africans comes after Mr. Trump signed an executive order suspending refugee admissions when he came into office. Then, in February, Mr. Trump created an exception for the resettlement of Afrikaners, while also cutting all U.S. financial assistance to South Africa.

Mark Hetfield, the president of HIAS, a Jewish resettlement agency, said his organization was committed to welcoming Afrikaners.

“But we are profoundly disturbed that the administration has slammed the door in the face of thousands of other refugees approved by D.H.S. months ago, notwithstanding courts ordering the White House to let many of them in,” Mr. Hetfield said, referring to the Department of Homeland Security. “That’s just not right.”

Supporters of such measures say they are necessary to undo the vestiges of colonialism and apartheid, when the white-minority government brutally repressed Black South Africans and drove them off their land. The South African government has sparred with Mr. Trump and his officials, saying that they are spreading misinformation.

Within weeks of announcing that Afrikaners would be eligible for refugee status, the administration deployed teams to Pretoria, the South African capital, to screen White South Africans for consideration, according to the documents obtained by The Times. The teams studied more than 8,000 requests from people expressing interest in becoming refugees, and the U.S. government identified 100 Afrikaners who potentially could be approved. Trump administration officials have been directed to focus particularly on screening White Afrikaner farmers.

The resettlement of refugees is normally funded in large part by the State Department. But Mr. Trump suspended that program when he came into office.

So the administration will be relying more on another agency that has traditionally supported refugees: a refugee office in the Department of Health and Human Services. That office has been reaching out to organizations assisting refugees in recent days to prepare them for the arrival of the Afrikaners, according to a department memo obtained by The Times.

Advocates for refugees said the rapid mobilization to allow the Afrikaners to resettle highlighted the administration’s inaction on other refugees, even sometimes in the face of court orders.

“Thousands of refugees from across the globe remain stranded in limbo despite being fully vetted and approved for travel, including Afghan allies, religious minorities and other populations facing extreme violence and persecution,” said Timothy Young, a spokesman for Global Refuge, a resettlement agency. “We hope this development reflects a broader readiness to uphold the promise of protection for all refugees who meet longstanding legal standards, regardless of their country of origin.”

Earlier this week, a federal judge ordered the Trump administration to lift the ban on refugees who were cleared for travel before Mr. Trump took office and to give them the opportunity to finally enter the country.

The rapid arrival of Afrikaners “flies in the face of the government’s claims that they aren’t able to process already-approved refugees, even after multiple courts have ordered them to do so immediately,” said Melissa Keaney, senior supervising attorney at the International Refugee Assistance Project, in a statement. “Thousands of refugees unlawfully stranded by President Trump’s refugee suspension are in limbo and are ready to restart their lives in the United States. There is no more time for excuses.”