On Tuesday, Senators Kelly Ayotte (R–NH) and Marco Rubio (R–FL) sent a letter urging President Obama to include restrictions on Iran’s long-range missile program during the P5+1 nuclear negotiations.

“An Iran with a nuclear weapons capability represents a grave threat to the United States and our allies,” wrote Ayotte and Rubio, “and an effective delivery system is a key element of a nuclear weapons capability. We believe the administration should not conclude any nuclear accord with Tehran without addressing the threat that Iranian ballistic missiles could pose to our nation.”

James Phillips, Heritage’s senior research fellow for Middle Eastern affairs, has also argued for taking a much tougher stance on Iran. Phillips argues that the U.S. should reject any agreement that “fails to verifiably end Iran’s nuclear proliferation threat.” This includes halting Tehran’s uranium enrichment and facilitating the transfer of its stockpile of 20 percent enriched uranium to an outside power.

To effectively deal with Iran’s advancing missile capability, the U.S. should continue beefing up its missile defenses. Today, Iran has the largest number of deployed missiles in the Middle East and can pose a threat to U.S. and allied targets as far as southern Europe. Furthermore, Iran has continued its pursuit for long-range missiles capable of striking the U.S. homeland and could test one as early as next year.

To counter the Iranian missile threat, the U.S. should remain committed to developing a robust, layered missile defense system that features both land- and sea-based assets. Currently, the U.S. fields a collection of theater missile defense systems as well as regional defenses. To protect the homeland, the U.S. maintains 30 operational ground-based interceptors at Fort Greely, Alaska, and Vandenberg Air Force Base in California, with 14 additional interceptors set to come online by 2017. And in May, the House passed a spending bill for $20 million to study a potential third missile defense site on the East Coast specifically intended to defend against a potential Iranian missile launch.

As Phillips and Senators Rubio and Ayotte realize, it is clear that the U.S. should maintain a tough stance on Iran as negotiations continue. One way to secure this position is sustaining the ability to destroy Iranian missiles and protect lives.

Harrison Menke is currently a member of the Young Leaders Program at The Heritage Foundation. For more information on interning at Heritage, pleaseclick here.