Mr Entwistle, spoke in a meeting with officials of the Peoples Democratic Party (PDP) in Abuja on Wednesday.
He appealed to Nigerians to shun acts that could incite violence.
The US Ambassador said that the United States would support Nigeria because of the long standing relationship between both countries.
“From our own historical experience, we understand the importance of election. The United States will support the Nigerian people in their quest to ensure a credible and transparent election that they want and deserve.
“That is what we stand for and as part of that, I will try to be in touch with all parties to understand them, so that we can be knowledgeable about the electoral process here.
“I think it is incumbent on all of us to work towards this. History shows us that one election can make the difference. It may not happen overnight, but genuine change in every society is only possible in a true democratic process,” he said.
Entwistle encouraged potential party candidates to publicly commit themselves to ensuring that “they would not encourage, foment or engage in violence before, during and after the elections”.
He asked Nigerians to come out en masse to participate in the voting exercise .
On his part,the Chairman of the Peoples Democratic Party, Mr Adamu Muazu, said that the party remained committed to achieving credible elections in the country as exemplified in the just concluded Osun and Ekiti governorship elections and beyond.
“We will always present credible candidates who can win elections. We will continue to provide internal-driven democracy that will be driven by the people,” he said.
Mu’azu emphasied that President Goodluck Jonathan had continued to insist on a “one man, one vote”process which he said the party was proud of.
“We will, by the grace of God, work for the people of Nigeria. Our leader, the President has through our party, been campaigning that voting should be one man one vote.
“We take time to advertise this in national dailies to make sure that we will continue to have cordial relationship with the people and the international community,” he stressed.