President Lee Myung-bak urged North Korea on Monday to end its pursuit of tensions with South Korea and choose the \"path of peace and prosperity,\" saying Seoul will make persistent efforts for peace with the communist nation. \"North Korea should break away from the path of confrontation and conflict and come out on to the path of peace and prosperity,\" Lee said during a Memorial Day speech at the National Cemetery in Seoul. \"For this, we will continue to make sincere and consistent efforts with patience.\" Relations between the two sides have been tense since President Lee took office in early 2008 with a policy to link unconditional aid to progress in international efforts to get North Korea to give up its nuclear programs. Their ties frayed further after the North\'s two deadly attacks on the South last year. Seoul has since demanded an apology from the North for the attacks as a key precondition for resuming reconciliation and restarting international nuclear disarmament negotiations. The South has also demanded that Pyongyang take concrete steps to demonstrate it is serious about giving up its nuclear ambitions. Last week, Pyongyang claimed that the South begged for summit talks when the two sides met secretly last month. South Korean officials denied the claim, saying the contact was to seek an apology from the North for the two attacks. The North\'s revelation of secret talks with the South was seen as a grave breach of diplomatic protocol to keep such contact confidential. That raised speculation that Pyongyang has given up on any hope of improving relations with the South. During the speech, Lee also said the South should be prepared for unification with the North. Lee has stressed the importance of bringing the divided Korean states together, saying unification is \"not a matter of choice but a must\" that should be sought at any cost because it will provide the Korean people with a springboard to prosperity. Lee has also said that unification with the communist nation could come at any time. The two Koreas fought the 1950-53 Korean War that ended in a cease-fire, not a peace treaty, leaving the sides still technically at war and their border one of the world\'s most heavily fortified. Lee said that the South will make sure to protect the values of free democracy, market economy and the rule of law. Lee also said that the government will implement better welfare measures for the patriots, providing them with greater support in employment, education, medical and housing matters. Lee said that the government will never stop searching for the remains of 130,000 South Korean soldiers killed in the Korean War and will \"make utmost efforts until the day comes when the last set of remains is found.\" After the ceremony, Lee visited the defense ministry team tasked with searching for the remains of missing soldiers and told officials there to redouble their search efforts.