U.S. immigration officials said yesterday that if the number of illegal immigrants applying for amnesty continues at the current rate of almost 40,000 a week, at least 2 million people will apply before the one-year program ends.

Immigration and Naturalization Service Commissioner Alan C. Nelson said at a news conference that as of July 16, a total of 305,419 persons had applied for amnesty, which under the new federal immigration law is available to illegal immigrants who can prove they arrived here before Jan. 1, 1982.

On hand were Tongchai and Puntipa Vongchan of Wheaton, and their children, aged 2 and 4, who were the first of 650 persons nationwide to receive temporary residency cards, the preliminary step to applying for permanent residency 18 months from now.

Nelson said between 35,000 and 40,000 persons were applying for amnesty each week, as opposed to just 4,200 during the week the program started in May. Critics said then that the low numbers indicated the program was failing.

INS had predicted that nearly 80 percent of applicants would file through community-based agencies enlisted to help in the amnesty effort, but so far only 10 percent of applications have come through this route. Nelson said he expected that number to increase.