The move is unlikely to gain momentum, however. Republicans dominate Congress and have so far show no willingness to turn on their president, and Mr Sherman does not even have the backing of many fellow Democrats.

The 62-year-old acknowledged that filing the article is "the first step on a very long road."

"But if the impulsive incompetency continues, then eventually - many, many months from now - Republicans will join the impeachment effort," he said in a statement.

Democratic leaders have distanced themselves from the efforts to impeach, believing it serves only to energise the president's supporters.

Mr Sherman's resolution has one co-sponsor, fellow Democrat Al Green of Texas.