The head of the Department of Homeland Security said Sunday that the Obama administration will "stem the tide" of migrants that's overwhelmed the southern border.Critics on both sides of the aisle have hammered President Obama's response to the crisis, arguing that his administration is doing too little too late to manage the wave of immigrants – many of them unaccompanied children – that's swelled in recent months.

But department Secretary Jeh Johnson said the administration is taking numerous steps that will discourage the trend and bring the border under control."The numbers have very definitely gone up," Johnson said Sunday on NBC's "Meet the Press" program. "But I believe we will stem this tide."Johnson pointed specifically to several areas where he said the administration has made progress in recent months. For example, the turnaround time for processing illegal immigrant adults without children has been reduced from 33 days to four days, he said.In addition, he said the government is taking on the Central American smuggling operations that have reportedly encouraged the migrant wave, while also making greater efforts to inform the migrants that they're not eligible for certain programs allowing them to remain legally in the United States."Our border is not open to illegal migration," he said.Republicans have blamed Obama for the crisis, pointing specifically to his Deferred Action for Childhood Arrivals program, which allows some undocumented immigrants brought to the country as children to remain and work without fear of deportation.But Johnson was quick to note that the program explicitly limits eligibility to those having lived in the United States continuously since 2007."The deferred action program is for kids who came to this country seven years ago," Johnson emphasized. "It's not for anyone who comes to this country today, tomorrow or yesterday."Johnson blamed deteriorating conditions in Honduras, El Salvador and Guatemala for the spike in numbers."The push factor is what's driving this recent influx," he said.Johnson also blamed Congress for failing to address the issue by passing an immigration reform bill – legislation Obama and the Democrats contend would ease pressure at the border.While the Senate passed such a proposal with bipartisan support last summer, House GOP leaders have shown little appetite for following suit.The congressional inaction has led immigration reform advocates on and off Capitol Hill to urge Obama to take whatever administrative steps he can to address the nation's broken system.Johnson on Sunday vowed to do just that."If Congress doesn't act," he said, "we will."