Reporting from Washington— As drug cartels wreak murderous havoc from Mexico to Panama, the Obama administration is unable to show that the billions of dollars spent in the war on drugs have significantly stemmed the flow of illegal narcotics into the United States, according to two government reports and outside experts.

The reports specifically criticize the government's growing use of U.S. contractors, which were paid more than $3 billion to train local prosecutors and police, help eradicate fields of coca, operate surveillance equipment and otherwise battle the widening drug trade in Latin America over the last five years.