Li, who is on an official visit to Japan, made the remarks when meeting with some of the former Japanese politicians who had participated in the treaty-making process on Thursday morning.
He hailed in particular the two countries' commitment to promoting free trade.
He added that the consensus reached between regional major countries - including China and Japan - on the Korean Peninsula issue is particularly important.
Qinduo Xu, a senior researcher at the Pangoal Institution.
Japan fears that any deal struck with North Korea will ignore its concerns, while China is working hard to make sure that Kim Jong Un doesn't move out of its sphere of influence.
But the past year has seen something of a rapprochement between the two, including the first phone call between Abe and Xi earlier this month.
At a reception marking the 40th anniversary of the treaty in Tokyo, Li said, this is the best possible way to commemorate the signing of China-Japan Treaty of Peace and Friendship, Xinhua reported.
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He stressed that the creation of the China-Japan-South Korea free trade zone would "benefit not only East Asia, but also [would] have an external effect and stimulate negotiations on regional economic integration between the three countries and ASEAN [Association of Southeast Asian Nations]".
Mr Abe said the first meeting of the dialogue will take place when he visits China.
Abe saw Li off at New Chitose Airport later in the afternoon.
During their meeting in Tokyo on Wednesday, Abe and Li agreed that China will expand imports of farm products from Japan.
The four documents refer to the 1972 Sino-Japanese Joint Statement, the 1978 China-Japan Treaty of Peace and Friendship, the 1998 China-Japan Joint Declaration, and the 2008 joint statement on advancing strategic and mutually beneficial relations.
"There is a danger of a new arrangement in their region in which both Japan and China have an interest without their full participation". "It does not include the Senkakus", a Japanese government official said.
Since World War II, China and Japan have had a rocky relationship, often driven apart by lingering resentment over Imperial Japan's atrocities during the war. "As an educator, I hope our younger generations would be more future-oriented and regard each other as friends and most importantly, neighbors", he said.