* North Waziristan tribesmen vow revenge
* Militants' pact with Pakistan army possibly at risk
* Expansion of drone campaign into other tribal lands
By Javed Hussain
PARACHINAR, Pakistan, June 20 (Reuters) - Suspected U.S. drones fired missiles into Pakistan's Kurram region on Monday and killed at least seven militants, local officials said, in the first strike in the lawless tribal region in a recently stepped up campaign by unmanned American aircraft.
