United States Senator Chris Coons said the Donald Trump administration would hold the Zimbabwean government responsible for the safety of Biti and other opposition members reportedly detained by the President Emmerson Mnangagwa administration after the July 30 polls.
Mnangagwa of the ruling Zanu-PF party won the presidential race with 50.8% of the vote - just enough to avoid a run-off against the MDC's Nelson Chamisa, who scored 44.3 percent. They were accompanied by Jameson Timba, the chief election agent for the party led by Nelson Chamisa.
"We have a good case and cause!" he tweeted shortly after filing the challenge.
MDC party lawyer Thanbani Mpofu last week said that theZimbabwe Electoral Commission's figures "grossly, mathematically fail to tally".
Chamisa is accusing the Zimbabwe Electoral Commission (ZEC) of doing a poor job in supervising over a free and fair election.
The Constitutional Court now has 14 days to rule on the legal challenge by the Movement for Democratic Change (MDC).
The conduct of the election was largely deemed sound by worldwide monitors, but representatives of the European Union noted Mr Mnangagwa, a former long-time Mugabe ally, benefited from an "un-level playing field" and some voter intimidation.
The first election since Robert Mugabe was forced to resign after a coup in November had been expected to end Zimbabwe's pariah status and launch an economic recovery but post-election unrest has reminded the country of its violent past.
Two days after the vote, six people were killed in an army crackdown on protests against the victory by Mnangagwa's ruling ZANU PF party.
While addressing a Zanu-PF Umguza and Bubi constituencies' inter-district meeting in Bulawayo, Mpofu said democracy prevailed in the just ended elections.
Biti asserted before the electoral commission's official announcement that Chamisa was the real victor. If it does this successfully, the court could order a recount or nullify the result altogether.