He would simply use projected budget surpluses to keep the system going until 2050, by paying down national debt and allocating the equivalent of the interest saved to the Social Security system.

ECONOMIST: Social Security

Since interest paid to the Fed, the Social Security system and other government pension funds is effectively rebated to the Treasury, taxpayers currently bear only the burden of interest on 60% of this debt.

WSJ: Phil Gramm and Steve McMillin: The Debt Problem Hasn't Vanished

But, again, we have our interests that we're very clear with the Russians about, which is that we believe there's a national security interest for the United States and our NATO allies to pursue this missile defense system.

WHITEHOUSE: Press Briefing