President Trump tweeted Monday night that Immigration and Customs Enforcement (ICE) will begin deporting "millions" of undocumented migrants next week.

Why it matters: There have been more border arrests so far this fiscal year than in any other full fiscal year in the past decade, with close to 600,000 migrant arrests. Immigration agencies have been struggling to care of the large numbers of families and children, mostly from Honduras, El Salvador and Guatemala. Many families are quickly released into the U.S. due to lack of space, Axios' Stef Knight notes.

By the numbers: The latest ICE figures show for the third month in a row, there were more than 100,000 border crossings — 144,278 in total.

What they're saying: Mexican Foreign Minister Marcelo Ebrard told a news conference last week Mexico and the U.S. had agreed to monitor migration in upcoming months, with a contingency for discussions on further asylum reforms if it was determined that individuals crossing the U.S. southern border had not been reduced.

Go deeper: Chart: How immigration levels in the U.S. have changed since 1900