12日，美朝首腦新加坡峰會發表聯合聲明。雙方就美朝建立新型關係、構建半島和平機制、實現全面無核化和尋找戰俘與失蹤人員遺骸等目標達成一致。雙方還承諾將就落實峰會協議進行後續協商。毫無疑問，此次峰會對緩和東北亞局勢，開啟半島無核化進程和建立和平機制具有重要意義。

回望半島無核化20多年的歷史，不難發現達成協議不容易，而落實協議則更困難。無論是1994年10月美朝達成的《美朝框架協議》，還是六方會談中所形成的三份文件，即2005年的《9•19共同聲明》、2007年的《2•13共同文件》和《10•3共同文件》，都歷經反覆和周折才“修成正果”，為解決朝核問題提供了路線圖。但是，由於這樣或那樣原因，沒有一張路線圖是走得通的，半島局勢卻一再陷入緊張狀態。

要解決落實難問題，歷史和本次峰會為人們提供了值得借鑒的重要經驗教訓。

一是建立互信，對話解決分歧。美朝新加坡峰會確定了解決朝核問題的大方向，雙方在實現這個目標過程中出現分歧甚至反覆在所難免。如何進行良性互動，通過對話解決分歧，而不是渲染分歧綁架整個朝核問題解決進程，不但需政治意願，還需要解決問題的智慧和技巧。此次聯合聲明中使用“全面無核化”取代美方一直堅持的“完全的、可驗證的、不可逆的無核化”便是一個很好的例證。

二是排除干擾，避免節外生枝。美朝新加坡峰會是向解決朝核問題邁出的第一步，雙方在以後的合作中應始終聚焦半島無核化和建立和平機制，而不是節外生枝，將次要問題與主要議題掛鉤。在《9•19共同聲明》發表之後，美方在毫無預兆的情況下指責朝鮮在澳門銀行“洗錢”，接着又宣布對朝方實施金融制裁，從此朝核問題進入“制裁－試驗－再制裁－再試驗”惡性循環的怪圈。面對問題應做減法，將次要問題與主要問題剝離，分開處理，而不是做加法。不分主次把所有問題都攪和在一起，只會增加解決問題的難度。

三是細節決定成敗。解決朝核問題是一項龐大的系統工程，而美朝新加坡峰會僅僅為這個系統工程確定了基本目標。如何將這些目標轉化成現實，還有大量細緻工作要做。例如，半島全面無核化與美朝建立新型關係、建立半島和平機制是什麼關係？孰先孰後，還是同步對等進行等等，都需要雙方直面問題，換位思考，相向而行，才能形成共識。歷史表明，往往一項細節沒有得到落實，就有可能導致整個協議失敗。

四是防止美黨派政治干擾。克林頓總統執政後期，美朝關係正常化大門一度打開了一條細縫。雙方高層官員實現了互訪，並就朝核、互設外交代表處等問題進行探討。然而，新上任的小布殊政府並沒有沿襲其前任的對朝政策。他在競選期間就不斷抨擊《美朝框架協議》，後又在國情咨文中將朝鮮列為“邪惡軸心”國家，接着又發現朝方研發以鈾為原材料的核武器。小布殊政府認為朝鮮背棄了《美朝框架協議》，由此宣布終結雙邊談判，而朝方也宣布將重啟根據框架協議凍結的核活動，並正式退出《不擴散核武器條約》。奧巴馬總統上台後又對朝推行“戰略忍耐”政策，對朝“施壓”多於接觸，美朝關係進一步惡化。美國黨派政治在對朝政策問題上的不確定性可見一斑。種種跡象表明，此次開啟的半島無核化進程不會是“一步到位”，而將是一個分階段推進的長時間過程。對美國政府來說，避免國內黨派政治干擾將是一個嚴峻挑戰。

五是朝韓和解是解決朝核問題的基礎。2010年爆發的“天安號事件”加劇了韓美對朝鮮的不信任感和對立情緒，並造成半島局勢再度滑向新的緊張狀態。相反，此次美朝新加坡峰會之所以能如期舉行，與超級“中間人”韓國總統文在寅在美朝之間穿梭斡旋是分不開的。正反兩方面經驗都說明，沒有朝韓和解，就談不上朝核問題的最終解決。

可以說，朝核問題是冷戰遺留的最後一道未解難題。在1994年、2005年和2007年，半島上空曾分別亮起解決這個問題的希望之光，但是曇花一現，很快就熄滅了，國際社會期待美朝新加坡峰會避免前幾次談判的覆轍。達成的協議貴在落實，雙方要全力以赴把協議轉化為現實，走好走穩半島無核化和永久和平的每一步。

US and North Korea leaders issued a joint declaration on June 12, announcing consensuses on building a new type of relationship, formulating peace mechanisms for the Korean Peninsula, realizing all-round denuclearization, and searching for the remains of prisoners of war and missing persons. The two parties also promised to conduct follow-up consultations to implement such agreements. Undoubtedly the summit holds special significance for easing tensions in Northeast Asia, opening a process of denuclearization, and building peace mechanisms.

Given the history of denuclearization talks over the past two decades, the consensuses have not come easily, and their implementation will prove even more difficult. From the October 1994 US-DPRK framework agreement to the three joint documents issued in 2005 and 2007, all similar agreements have undergone ups and downs and offered roadmaps for resolving the Korea nuclear crisis. Yet none worked in the end, and tensions persisted.

History and the latest summit both provide important lessons for making the agreements work.

First, build mutual confidence, resolve differences through dialogue. The Singapore summit set the general direction for resolving the Korea nuclear crisis, but the two sides can't avoid differences and reversals in accomplishing that goal. It calls for both political will and wisdom to engage in benign interaction and resolve differences via dialogue, instead of highlighting divergences and taking the process hostage. The joint declaration's substituting the US side's persistent idea of “complete, verifiable, irreversible denuclearization” for “all-round denuclearization” was a fine example.

Second, eliminate disruptions, avoid unexpected complications. After the inspiring first step toward denuclearization taken at the Singapore summit, the two should concentrate on the matter and the building of peace mechanisms, rather than associate secondary issues with core concerns. Mingling main and secondary topics will make things thornier. Following the September 19, 2005 Common Declaration, the US side suddenly accused North Korea of money-laundering at the Bank of Macau and imposed financial sanctions against it, the Korea nuclear issue has since been mired in the vicious circle of “sanctions – tests – new sanctions – new tests”.

Third, details matter. The Singapore summit just set the goal for the complicated Korea nuclear issue, which entails sophisticated systems engineering. A lot more needs to be sorted out. For instance, what is the relationship between all-round denuclearization and new bilateral relations and peace mechanisms? Which should come first? Judging from previous experiences, one failed detail may result in the collapse of the entire agreement.

Four, prevent distractions from US partisan politics. There was a thin ray of hope in the second half of the Clinton presidency. There had been exchanges of visits by ranking officials, as well as consultations on the nuclear issue and the opening of representative offices. George W. Bush ended the negotiations after assuming office, North Korea re-activated nuclear activities that had been frozen under the framework agreement, and formally withdrew from nuclear non-proliferation. Bilateral ties worsened under the Obama administration, as Washington put more emphasis on pressuring Pyongyang than engaging with it. The newly initiated denuclearization process will be an incremental, long-term process, and it will be a severe challenge for the US government to deal with the influence of partisan politics.

Fifth, North-South reconciliation is the foundation for resolving the Korean nuclear issue. The Singapore summit would not have been possible without the arduous brokering by ROK President Moon Jae-in, the super “middleman”. Past vicissitudes show that ultimate resolution of the nuclear issue would be out of the question without the two Koreas getting along.

The Korea nuclear issue is the last unresolved puzzle the Cold War left behind. There had been sparks of hope in 1994, 2005, and 2007, but they vanished very soon. The international community hopes the Singapore summit can avoid the fate of past endeavors. For that to happen, the two parties should put in more efforts to implement what has been agreed on, and make sure every step forward is solid.