Homeland Security Secretary Jeh Johnson said Monday that the "worst is over for now" in the immigration crisis along the southern border as the number of unaccompanied children apprehended entering the United States illegally dropped in August to its lowest level in 1 1/2 years.

A total of 3,141 children were detained by Border Patrol agents last month, well below the peak of more than 10,000 in each of May and June, when the unprecedented influx prompted President Obama to declare a humanitarian crisis. It continued a steady decline over the past two months, as administration officials have stepped up efforts to stem the flow of unauthorized immigrants from Central America and Mexico.

Homeland Security Secretary Jeh Johnson during a press conference June 30 in Edinburg, Texas. (AP Photo/The Monitor, Nathan Lambrecht)

Johnson said the Obama administration is asking Congress for $1.2 billion in fiscal 2015, which begins Oct. 1, to deal with the more than 132,000 immigrants who have already crossed the border illegally over the past year -- most of whom remain in the United States awaiting deportation hearings. The administration has begun deporting adults, but the unaccompanied minors have greater protections under U.S. immigration laws and court hearings are backlogged significantly.

Obama had asked Congress for $3.7 billion in emergency funding to care for the immigrants and speed up their deportations by adding more immigration judges. But Congress adjourned for a five-week summer recess last month without approving additional resources.

The number of immigrant who attempt to enter the United States illegally has traditionally dropped in the summer months, in part due to high temperatures, but administration officials expressed cautious optimism that the government's increased efforts -- including pressure on foreign governments and advertising in Central American countries -- had helped stem the flow.

"Though the worst is over for now," Johnson said in a statement, "there are still bills to be paid and our border security efforts must be sustained to prevent another spike like we saw this year."