STOCKHOLM (Reuters) - The United States and Sweden on Tuesday signed a Defence Cooperation Agreement, the U.S. Department of State said, as the Nordic country strengthens military alliances while waiting for approval to join NATO.

"Sweden is a strong, capable defense partner that champions NATO's values, and will further strengthen the Alliance once its NATO accession is completed," the State Department said in a written statement. "Sweden's membership will strengthen our collective defense and enhance our ability to respond to security challenges in the Euro-Atlantic area."

Swedish Defense Minister Pal Jonson said he was hopeful that accession would happen "as soon as possible", but would not give any estimate when Turkey and Hungary - the only two NATO members not to give Sweden the green light yet - would add their support.

(Reporting by Simon Johnson and Dan Whitcomb; Editing by Christina Fincher and Jacqueline Wong)