Obama, Federal contractors, and living wages

Workers for Federal contractors at the Pentagon and several other government-owned buildings have gone on strike because of the low wages being paid. They have asked the administration for help.

President Obama has recently called called for a minimum wage increase to $10 or more per hour. Can he not, by executive order, force government contractors to pay living wages? If this is not possible with not current contacts, can he force agencies negotiating new contracts or renewing contacts to include language about a a minimum wage and perhaps decent health insurance?