SEOUL (Reuters) – South Korea dismissed on Monday a North Korean proposal for military talks as “a bogus peace offensive” and said it was formally rejecting the overture because it lacked a plan to end the North’s nuclear program.

North Korea’s proposal on the weekend for talks between the two Koreas, a repeat of a call by North Korean leader Kim Jong Un at a congress of his ruling party this month, came after a period of heightened tension on the peninsula.

North Korea conducted its fourth nuclear test in January and launched a long-range rocket in February, triggering tougher international sanctions and the adoption of a more hardline position by South Korean President Park Geun-hye.

North Korea said dialogue between military officials from the two sides was urgently needed to reduce tension, and suggested they be held in late May or early June.

South Korea said the offer was insincere.

“The dialogue proposed by the North does not mention its nuclear program, which is the fundamental issue for peace on the Korean peninsula and South-North ties,” South Korean Defence Ministry spokesman Moon Sang-gyun told a briefing.

“Proposing dialogue without an expression of its position on denuclearization is a bogus peace offensive for bogus peace that lacks sincerity.”

Moon said the South had sent a message over a military hotline on Monday expressing regret over the North’s proposal and asking it to state its position on denuclearization.

This month, at the first congress of North Korea’s Workers’ Party in 36 years, Kim declared his country a nuclear weapons state and vowed to press on with nuclear development, which he said was defensive.

In the run-up to the congress, North Korea test-fired a series of missiles including a submarine-based ballistic missile. It also attempted a launch of an intermediate-range ballistic missile.

South Korea’s Unification Ministry, which handles political ties with the North, said Pyongyang’s intention may be to sow discord among the public in the South and create a rift in the international commitment to sanctions.

“Let me repeat: Now is not the time for dialogue,” said ministry spokesman Cheong Joon-hee.

North Korea came under tougher international pressure with the March adoption of a U.N. Security Council resolution that was even backed its lone major ally China, which disapproves of its nuclear arms program.

South Korea has also cut off all commercial contacts with the North.

The two Koreas have remained in a technical state of war since their 1950-53 conflict ended in a truce, not a peace treaty.

(Reporting by Jack Kim)