Sen. Ted CruzRafael (Ted) Edward CruzOvernight Finance: GOP criticism of tax bill grows, but few no votes | Highlights from day two of markup | House votes to overturn joint-employer rule | Senate panel approves North Korean banking sanctions GOP criticism of tax bill grows, but few ready to vote against it Anti-gay marriage county clerk Kim Davis to seek reelection in Kentucky MORE (R-Texas) said securing the borders was crucial to stopping Islamic terrorists from launching an attack on U.S. soil.

“It is beyond time for us to secure our borders,” Cruz said on the Senate floor Monday. “As long as our border isn’t secure, we’re making it far too easy for terrorists to follow through on promises [to attack the United States].”

Cruz said he is concerned about the terrorist group the Islamic State in Iraq and Syria (ISIS), which is gaining control over territory in the Middle East. The group has already killed two American journalists and has threatened to use U.S. citizens who support their cause to launch attacks.

On Monday, Cruz introduced the Expatriate Terrorist Act, which would revoke the U.S. citizenship of anyone fighting or providing support to ISIS.

“ISIS is a study in oppression and brutality,” Cruz said. “We should take common-sense steps to make fighting for ISIS a formal renunciation of U.S. citizenship.”

House Republicans have introduced similar legislation.

Cruz blasted President Obama for seeking a “utopian” leadership agreement in Iraq instead of dealing with the threat of ISIS. He said Obama should come to Congress to seek military authority to combat ISIS.

“The objective here is to protect the national security interest of the United States and to destroy terrorists who have declared jihad on our nation,” Cruz said. “I ask the president to reconsider both of these points.”

Cruz is considered a potential GOP presidential nominee in 2016.

— This article was updated on Sept. 9, at 12:40 p.m.