brussels u.s. president donald trump tell fellow nato leaders thursday unite state would never stop fight terrorism call manchester attack savage barbaric also accuse low-spending members alliance owe massive amount money nato trump say ally would drive militants urge nations never waiver determination defeat terrorism achieve last security prosperity peace trump say unveil memorial sept.11 2001 attack new york washington nato headquarter terrorism must stop ... horror saw manchester many place continue forever trump say refer monday suicide bomb northern english city kill 22 people include children trump nato vow unwavering fight terrorism