SEOUL, Jan 4 (Reuters) - South Korean President Yoon Suk-yeol said on Wednesday he would consider suspending a 2018 inter-Korean military pact if the North violates its airspace again, his office said, amid tension over a recent intrusion by North Korean drones.Yoon made the comment after being briefed on countermeasures to North Korean drones that crossed into the South last week, calling for building an "overwhelming response capability that goes beyond proportional levels," according to his press secretary, Kim Eun-hye.The 2018 deal, sealed on the sidelines of a summit between North Korean leader Kim Jong Un and South Korean President Moon Jae-in, calls for ceasing "all hostile acts", creating a no-fly zone around the border, and removing landmines and guard posts within the heavily fortified Demilitarised Zone.Inter-Korean relations have been testy for decades but have grown even more tense since Yoon took office in May pledging a tougher line against Pyongyang.To boost its anti-drone capability, the ministry announced plans last week it would spend 560 billion won ($440 million) over the next five years on technology such as airborne laser weapons and signal jammers."