At least 67 people have died in clashes since October when an 18-party opposition movement launched a wave of protests calling on Prime Minister Sheikh Hasina to resign before the January 5 polls.
The opposition, led by Hasina's bitter rival, Khaleda Zia, fears the premier will try to rig the vote in a country which for decades has been plagued by coups and political upheaval.
"We believe the need is now even more urgent for the major political parties to engage immediately in constructive dialogue, to find a way forward, to hold elections that are free, fair and credible," said deputy State Department spokeswoman Marie Harf, yesterday.
In the latest incident, suspected opposition activists on Wednesday derailed a train in northern Gaibandha by removing metal links holding the tracks together, killing at least three people and injuring dozens.