The White House is vigorously defending President Donald Trump's immigration restrictions, as protests spread throughout the country. Some Republicans in Congress urged caution amid legal challenges to the order banning travelers from seven predominantly Muslim countries, though top congressional Republicans remain largely behind the new president. In a background call with reporters on Sunday, a senior administration official declared the order's implementation "a massive success story," claiming it had been done "seamlessly and with extraordinary professionalism." That, despite widespread confusion and an apparent walk-back about how the order, which temporarily bars the citizens of seven majority Muslim nations from entering the US, would be applied to certain groups, like US legal permanent residents. Homeland Security Secretary John Kelly issued a statement on Sunday saying that, absent information indicating a serious threat to public safety and welfare, residency would be a "dispositive factor in our case-by-case determination." That means citizens of the seven countries who hold permanent US residency "green cards" will not be barred from re-entering the US, as officials had previously said. It remains unclear what kind of additional screening they will now face. Trump's order, which also suspends refugee admissions for 120 days and indefinitely bars the processing of refugees from Syria, has sparked widespread protests and denunciations from Democrats and a handful of Republicans. Many have accused the administration of rushing to implement the changes, resulting in panic and confusion at the nation's airports. "You have an extreme vetting proposal that didn't get the vetting it should have had," said Sen. Rob Portman, R-Ohio, who urged the new president to "slow down" and work with lawmakers on how best to tighten screening for foreigners who enter the United States. "In my view, we ought to all take a deep breath and come up with something that makes sense for our national security" and reflects the fact that "America's always been a welcoming home for refugees and immigrants," he said. Several Democrats in Congress said they would be introducing legislation to stop the ban. White House adviser Kellyanne Conway said the changes were "a small price to pay" to keep the nation safe. But it's unclear whether the order will accomplish that. The order does not address homegrown extremists already in America, a primary concern of federal law enforcement officials. And the list of countries in Trump's order doesn't include Saudi Arabia, where most of the Sept. 11 hijackers were from. Trump, meanwhile, defended his actions, insisting it was "not a Muslim ban, as the media is falsely reporting." Top congressional Republicans, meanwhile, were backing Trump despite concerns raised on Sunday from a handful of GOP lawmakers and condemnation from the Koch political network, which is among the most influential players in the conservative movement. Republican Sens. John McCain and Lindsey Graham warned of unintended consequences, expressing fear the order could "become a self-inflicted wound in the fight against terrorism." "This executive order sends a signal, intended or not, that America does not want Muslims coming into our country. That is why we fear this executive order may do more to help terrorist recruitment than improve our security," they wrote. Trump fired back on Twitter, calling the pair "sadly weak on immigration."