The central government lobbied in support of Taiwan's bid to keep its seat at the United Nations ahead of the 1971 General Assembly, at which China became a member, according to Japanese diplomatic documents declassified on Thursday.

One of the documents also indicates Japan offered to provide economic assistance to a country in return for supporting Taipei's bid to keep its U.N. seat. At the assembly, however, Taiwan lost its seat.

While support for Beijing was spreading among member states, then-Prime Minister Eisaku Sato announced on Sept. 22, 1971, that Japan would support two joint proposals, including one that would have required a more than two-thirds majority of votes for Taiwan to lose its seat, rather than a simple majority.

But the Japanese Foreign Ministry then predicted that members opposed to that proposal surpassed supporters by 58 to 55 as of Sept. 22, prompting Japan to seek support from other member states.

A classified cable dated Oct. 5, 1971, shows Japan decided to help Malta, which had not revealed its position, to build a bridge and an undersea tunnel in an effort to secure the Mediterranean island state's support for the two-thirds vote proposal.

Japan also sent messages from the prime minister to around 10 nations, while then-Foreign Minister Takeo Fukuda met his Belgian counterpart, as Brussels was in talks with Beijing to normalize bilateral ties.

On the day of the vote on Oct. 25, the Foreign Ministry expected supporters of the proposal to prevail by 60 to 58 while 13 members were likely to abstain.

But the proposal was voted down with opponents surpassing supporters by 59 to 55, while 15 members including Malta and Belgium chose to abstain.

Belgium established diplomatic relations with China the same day.

Immediately after the voting, another resolution to approve Taiwan's withdrawal from the United Nations was adopted by a majority vote.