On Thursday his office said the number of migrants apprehended, or deemed inadmissible, on the US border with Mexico fell to 82,049 in July, down 21 per cent from June.
Mr McAleenan said: “The situation is improving by every available metric but, I want to be very clear, that we remain at and beyond crisis levels in illegal crossings.”
Moments after Mrs Pelosi’s delegation arrived in Guatemala, more than 200 Guatemalans deported from the US touched down on two separate planes.
They were among nearly 35,000 Guatemalans deported from the US so far this year.
While in Guatemala Mrs Pelosi was due to visit a children’s shelter and meet with human rights activists, and government officials.
Mr McAleenan said that, in July, the number Guatemalans crossing the US border was down 41 per cent from the previous month.
The numbers from El Salvador fell 21 per cent, while the amount of Hondurans was down 16 per cent.
He said the decline was largely due to an agreement signed with Mexico in June to stem illegal migration through it from other countries.
Mr McAleenan said: “Just two months ago we apprehended or encountered 144,000 individuals crossing our border illegally or presenting without documents – the highest monthly total in 13 years. In July, that number was 82,000.”