Spain and the United States agreed to ramp up co-operation against terrorism and organised crime during a visit here on Tuesday by US Attorney General Alberto Gonzales, the interior ministry said.
The agreement came during talks between Gonzales and Spanish Interior Minister Alfredo Perez Rubalcaba, it said.
Washington offered to make technology which the US Federal Bureau of Investigation uses to index DNA samples available to Spanish police.
Spanish Justice Minister Juan Fernando Lopez Aguilar told reporters after the meeting, which also saw Gonzales confer with Spanish counterpart Candido Conde-Pumpido, that judicial co-operation between the two nations was "excellent."
He added that they were committed to "achieving good long-term results" in fighting terror.
Gonzales said the United States was sometimes "misunderstood" in Europe and it had to "talk more" to explain its position on security.
Asked if Spain was prepared to countenance handing over terror suspects to US military courts, Aguilar told Spanish media that Spain was determined to protect its citizens' rights at all times.
Gonzales did not address a decision last year by the Spanish Supreme Court to overturn a six-year prison sentence for al Qaeda membership handed down in October 2005 to a former Spanish inmate at the US base in Guantanamo Bay, Cuba.
In a separate case, the high court this month acquitted a Moroccan former inmate of Guantanamo who also had been accused of Al-Qaeda membership.