WASHINGTON - US President Barack Obama said on Thursday that he still planned to take steps on his own to improve the US immigration system but that his timeline for taking action has been affected by the need to deal with a flood of migrant children from central America.

Obama had previously said he planned by the end of summer to find ways to change immigration regulations, unilateral action he said was made necessary by the failure of Congress to pass comprehensive reforms.

But at a news conference on Thursday, Obama was circumspect about the timing of his announcement, which will be controversial ahead of November midterm elections where Democratic control of the US Senate is at stake.

Asked whether he would delay his decision on immigration changes, Obama talked about the time his administration has invested on apprehending migrant children, nearly 63,000 of whom have come across the southwestern border since October 2013.

"Some of these things do affect timelines, and we're just going to be working through as systematically as possible in order to get this done," Obama said.

"But have no doubt: in the absence of congressional action, I'm going to do what I can to make sure the system works better," he said.

In 2012, Obama gave temporary legal status to some undocumented immigrants who were brought to the United States as children. Hispanic groups have pressed him to expand that policy to millions of family members of those children.

But 70 percent of Americans believe undocumented immigrants threaten the nation's culture and economy, a Reuters/Ipsos poll showed earlier this month.

Immigration has been a hot issue for lawmakers at meetings in their home states this summer and Conservatives who object to Obama's immigration policies have threatened to tie a must-pass budget bill to the issue, raising the specter of a government shutdown.

But if Obama delays, that would infuriate Hispanic groups, an important base of support for Democrats.

CONCERNS ABOUT RENEWED SURGE

The numbers of children showing up at the border have dropped but could rise again when the summer heat dissipates. The White House wants to make sure that a high-profile announcement from Obama doesn't inadvertently spur a renewed surge of migrants.

"We don't want to see people resume taking this dangerous journey to the border in the coming months," a White House official said on condition of anonymity.

"The timing of any potential action on immigration could influence migrations to the border," the official said.

Democrats are wary ahead of November midterm elections. If they lose control of the US Senate, Obama would face setbacks for the final two years of his presidency.

There is anxiety about any controversy, including immigration, lest it tip the balance in key races, said Jim Manley, a Democratic strategist who is a former aide to Senate Democratic leader Harry Reid.

"I'm willing to say that I found his comments a bit odd and he seemed to suggest that there's a pretty big debate going on within the White House about when exactly is the right time to issue this executive order," Manley said in an interview.

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