The cable published online -- dated January 11, 2006 and marked "sensitive but unclassified" -- contains summaries of conversations Temer, a federal lawmaker at the time, had with the US officials.
WikiLeaks in a Twitter message claimed Temer acted as an "embassy informant for US intelligence." The cable is marked as cleared by the US embassy in Brasilia but does not name or give the ranks of the officials Temer briefed.
In the briefings, Temer spoke of possible plans for his centrist PMDB party to mount an electoral challenge to Brazil's leftist president at the time, Luiz Inacio Lula Da Silva, according to the summaries in the cable.
Temer stepped up from the post of vice-president to fill her role while the trial takes place.
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Rousseff called the move a "coup" and branded Temer a traitor for abandoning her governing coalition and supporting the impeachment drive against her.
Temer's government held its first cabinet meeting on Friday as it got to work to tackle Brazil's deep economic crisis.
Brazil hosts the Olympic Games in Rio de Janeiro from August 5 to 21.