Special counsel Robert Mueller believes it will take three weeks to present a case against former Trump campaign officials Paul Manafort and Rick Gates, according to court documents.
A filing made public in federal court in Washington by Mueller prosecutor Kyle Freeny estimates 15 trial days to present the case to a jury.
On Monday, Mr Mueller filed a 12-count indictment against Manafort, who served as Donald Trump's campaign chairman, and his deputy Gates.
The charges include violations of federal money laundering rules, foreign lobbying and banking laws.
Manafort and Gates have pleaded not guilty. They have been placed under house arrest and released on multimillion-dollar bonds.
In court papers, lawyers for Manafort called Mr Mueller's case "embellished", and asked a judge to ease the terms of his pre-trial confinement.
The accusations against Manafort and Gates were the first criminal charges stemming from Mr Mueller's six-month probe of potential ties between Russian operatives and the Trump campaign.
Another campaign-era aide, George Papadopoulos, has pleaded guilty to lying to FBI agents about his contacts with Russian agents during the 2016 presidential election and is co-operating with Mr Mueller's investigators, court records unsealed this week revealed.
Mr Mueller's charges against Manafort, 68, and Gates, 45, relate to their financial dealings while lobbying for pro-Russia political interests in Ukraine as far back as 2012.
Mr Trump wrote on Twitter this week that there was "NO COLLUSION" between his campaign and Russia and said the case filed against Manafort centred on acts that occurred "years ago", well before Manafort got involved with his campaign.