WASHINGTON — President Barack Obama is on pace this year to deport the fewest number of immigrants since at least 2007, even as he has postponed until after Election Day his promised unilateral action that could shield millions more from deportation.

According to an analysis of Homeland Security Department figures by The Associated Press, the federal agency responsible for deportations sent home 258,608 immigrants between the start of the budget year in October and July 28. During the same period a year earlier, it removed 320,167 people — meaning a decrease this year of nearly 20 percent.

Over the same period ending in July 2012, Immigration and Customs Enforcement deported 344,624 people, some 25 percent more than this year, according to the federal figures obtained by the AP.

The figures, contained in weekly internal reports marked “Official Use Only,” reflect the marked decline in deportations even as Obama has delayed announcing what changes he will make to U.S. immigration policies. Immigration advocates widely expect Obama to reduce the number of people who are deported, and that’s a particularly sensitive issue in many states, leading to his postponement of any action until after the November elections.

Obama sent his chief of staff to the Capitol on Thursday to reassure unhappy Latino lawmakers that he still plans to act by the end of the year. Lawmakers say some vented their anger during the meeting with Denis McDonough, who heard them out and pledged action.

Since Obama took office, his administration has removed more than 2.1 million immigrants.

There are two principal reasons why fewer immigrants already are being deported:

The Obama administration decided as early as summer 2011 to focus its deportation efforts on criminal immigrants or those who posed a threat to national security or public safety. Many others who crossed into the United States illegally and could be subject to deportation are stuck in a federal immigration court system. Last month the backlog in that system exceeded 400,000 cases for the first time, according to court data analyzed by the Transactional Records Access Clearinghouse at Syracuse University. For each case, it now takes several years for a judge to issue a final order to leave the U.S.

As Border Patrol agents detain more people from countries in Central America, not Mexico, the volume and circumstances of the cases take more time for overwhelmed immigration officials and courts to process because, among other reasons, the U.S. must fly such immigrants home rather than letting them walk back across the border into Mexico. A surge in the number of immigrant families, mostly women and young children, has swamped temporary holding facilities, leading the Homeland Security Department to release many people into the U.S. interior with instructions to report back to authorities later.

Asked for comment, Immigration and Customs Enforcement spokeswoman Gillian Christensen said the agency has not released removal numbers for this budget year and officials are “still assessing a number of factors that inform ICE’s ability to remove individuals.”

“ICE remains focused on smart and effective immigration enforcement that prioritizes the removal of convicted criminals and recent border entrants,” Christensen said in a statement.

Also, under U.S. law, immigrant children from Central America caught crossing the border alone can’t be subjected to speedy removal proceedings without appearing before a judge. The government interviews Mexican and Canadian children to make sure they aren’t trafficking victims; then they can be sent home quickly.

The administration instructed immigration officials starting in summer 2011 to prioritize deportation cases involving criminal immigrants. Deportations had been increasing since late 2008, but since that summer the overall number has dropped markedly.

It remains unclear exactly what actions Obama will announce after the elections. He said earlier this month that the U.S. would be better off if immigrants — who in some cases he said have been in the U.S. for longer than 10 years and have American children — “have a path to get legal by paying taxes and getting aboveboard, paying a fine, learning English if they have to.”

But there are limits under U.S. law to actions that Obama could take without approval from Congress. He can’t generally give large groups of immigrants blanket permission to remain permanently in the United States, and he can’t grant them American citizenship. He almost certainly could delay indefinitely efforts to deport immigrants already in the U.S. illegally, and he could give them official work permits that would allow them to legally find jobs, obtain driver’s licenses and file tax returns.

The president said this month that a partisan fight in July over how to address a surge in the number of immigrant children caught crossing the border had created the impression that there was a crisis — and a volatile climate for taking the measures he had promised.

Amid the crush of immigrant families and children caught traveling alone across the border, Homeland Security Secretary Jeh Johnson has promised that most will be sent home.

“Those who cross our border illegally must know there is no safe passage and no free pass,” Johnson said in July. “Within the confines of our laws, our values and our resources, they will be sent back to their home countries.”

As of early September, only 319 of more than 59,000 immigrants who were caught traveling with their families have been returned to Central America.