President Obama on Saturday defended his controversial executive action to grant temporary legal status to 4.1 million illegal immigrants, and challenged congressional Republicans to pass comprehensive immigration reform legislation.

In his weekly radio address, recorded in Las Vegas, Obama rebutted criticism from Republicans that his unilateral move overstepped the Constitution, while insisting that allowing undocumented immigrants whose children are U.S. citizens or legal residents to obtain work permits is not “amnesty.” Obama blamed House Republicans for forcing his hand, saying they could have prevented his executive action by approving the Senate-passed “gang of eight” immigration reform bill.