President Barack Obama says that the surge of immigrant children entering the US "illegally" has changed the politics surrounding the issue of immigration and led him to put off a pledge to use executive action that could have shielded millions of people from deportation.

Immigration reform advocates criticised Obama after White House officials said that the president would not act at summer's end as he promised in June but would take up the matter after midterm elections in November.

In a television interview taped for US channel NBC's "Meet the Press" on Saturday, Obama rejected the charge that the delay was meant to protect Democratic candidates worried that his actions would hurt their prospects in tough Senate races.

In his remarks to NBC, which were to be aired on Sunday, Obama said a partisan fight in July over how to address an influx of unaccompanied minors at the border had created the impression that there was an immigration crisis and thus a volatile climate for taking the measures he had promised to take.

"The truth of the matter is - is that the politics did shift midsummer because of that problem," he said.

"I want to spend some time, even as we're getting all our ducks in a row for the executive action, I also want to make sure that the public understands why we're doing this, why it's the right thing for the American people, why it's the right thing for the American economy."

Reflecting the passion behind the threat of deportations, immigration advocacy groups that have criticised Republicans for not passing an immigration overhaul instantly turned their anger on Obama.

'Slap to the face'

Cristina Jimenez, managing director of United We Dream, said the decision was "another slap to the face of the Latino and immigrant community".

Frank Sharry, executive director of America's Voice, said: "We are bitterly disappointed in the president and we are bitterly disappointed in the Senate Democrats.

"We advocates didn't make the reform promise; we just made the mistake of believing it.

"The president and Senate Democrats have chosen politics over people, the status quo over solving real problems."

Two White House officials said Obama made the decision to delay taking action as he returned on Friday to Washington from a NATO summit in Wales, the AP news agency reported.

He called a few allies from Air Force One to inform them of his decision, the officials, who spoke on condition of anonymity, said, and made more calls from the White House on Saturday.

'Politics at its worst'

Obama went to the White House Rose Garden on June 30 to angrily declare that House Speaker John Boehner had informed him that the Republican-controlled House would not be taking up any measures to overhaul the immigration system.

As a result, he said, he had directed Homeland Security Secretary Jeh Johnson and Attorney General Eric Holder to give him recommendations for executive action by the end of summer.

Obama also pledged to "adopt those recommendations without further delay."

By delaying, the White House appeared to be weighing the benefits of acting now and running the risk of immigration getting blamed for any Democratic losses, especially in the Senate where Democratic control hangs in the balance.

Republican leaders in Congress criticised the president, calling his decision a cynical ploy.

Senate Republican Minority Leader Mitch McConnell said Obama's move amounted to "Washington politics at its worst."

Source: Agencies