Seoul, Sep 27 : North Korea remained unresponsive to South Korea's calls via liaison and military hotlines on Monday despite cautious optimism created after the sister of Pyongyang's leader Kim Jong-un said the two Koreas could discuss improvement in long-strained relations. "North Korea did not answer our opening call through the South-North joint liaison office at 9 a.m.," Yonhap News Agency quoted a Unification Ministry official said. A official also said a call via the military hotline went unanswered. Kim Yo-jong, the powerful sister of the North Korean leader, issued two statements last week in which she said the two Koreas could discuss improvement in inter-Korean relations, re-establishment of the Kaesong liaison office and even a summit on conditions that Seoul drops its double-standard and hostile attitudes against it. The statements followed President Moon Jae-in's offer for a formal end to the 1950-53 Korean War in his UN speech. The Unification Ministry saw Kim's statements as positive and expressed hope for the resumption of cross-border communication and dialogue. Inter-Korean relations have remained in a deadlock since the no-deal summit between the US and North Korea in early 2019. The ties chilled further after North Korea blew up the Kaesong liaison office and cut off all cross-border communication lines in protest of anti-Pyongyang leaflets sent from the South. The lines were briefly back online in late July but the North has not answered Seoul's regular calls twice a day again as it bristled at joint military drills by South Korea and the US /IANS