DR Congo's powerful Roman Catholic Church has said it knows who has won the vote and urged the electoral commission to publish the "truth".
The combat troops and supporting military aircraft would provide security to United States citizens, personnel and diplomatic facilities in the Congolese capital, Kinshasa, should the need arise.
The government says the election was fair and went smoothly. "These deployed personnel will remain in the region until the security situation in the Democratic Republic of Congo becomes such that their presence is no longer needed", the letter stated.
CENI had wanted "to be able transmit the results from the voting machines to help us publish the results quickly but nobody wanted that procedure", he said.
The SADC's qualified endorsement countered allegations by opposition candidates that the December 30 vote was marred by widespread irregularities and criticism by a senior US lawmaker that the election was "neither free nor fair".
It can not say publicly who the clear victor appears to be, as Congo's electoral regulations forbid anyone but the electoral commission to announce results.
Elections to succeed him were delayed several times before they finally took place, and were further postponed in several areas hit by violence.
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CENCO said it deployed more than 40,000 observers to monitor Sunday's vote, the first presidential ballot since 2011.
Pre-election polling suggested Shadary was running behind opposition candidates Martin Fayulu and Felix Tshisekedi, but both sides have expressed confidence in a victory.
The delay has triggered an outcry from individuals home and overseas awaiting the results of the historic elections.
The meeting came even as the UN Human Rights office (OHCHR) termed the post-election environment in the DRC as "calm but tense" as the country waits for the results of the presidential poll. According to reports, more than one million people were prevented from voting in opposition strongholds, after the electoral commission cancelled the polls there citing an outbreak of Ebola.
In a major humanitarian developement on Friday, some 16,000 people from DRC have arrived in neighbouring Republic of the Congo - also known as Congo-Brazzaville - after fleeing deadly intercommunal clashes.
But after 18 years in power, critics say, Kabila is determined to hang on by securing a win for his chosen candidate Emmanuel Ramazani Shadary.