Jerrold Nadler said draft articles were already being prepared based on the evidence heard during the inquiry over the last months.
However, a decision on the final charges will not be made until after a public committee hearing on Monday.
Mr Nadler, a Democratic representative for New York, said the committee panel had “a lot to consider”.
“There are possible drafts that various people are writing,” he told CNN. “But the fact is we’re not going to make any decision as to how broad the articles should be, as to what they contain what the wording is – until after the hearing tomorrow.”
He said it was possible the panel could vote this week.
Monday’s televised committee hearing has been described by one official as a collision between the Democrats’ “world of facts” and with Republicans’ “world of conspiracy theories”.
Witnesses have told the impeachment inquiry Mr Trump sought to pressure Ukrainian president Volodymyr Zelensky into investigating his political rival, former vice-president Joe Biden.
He is said to have ordered the withholding of $391m (£298m) in military aid to Ukraine and a White House meeting until the probe was announced publicly.
Hundreds of law academics have signed a letter to Congress stating their belief that there is “overwhelming evidence” that the US president engaged in impeachable conduct.
Additional reporting by Reuters