The election body has rejected a move by Washington to adjust the results of next month's vote to benefit the Sunni community.
Speaking of "unacceptable" interference, Electoral Commission spokesman Farid Ayar said: "Who wins, wins. That is the way it is. That is the way it will be in the election."
Ayar was emphatic in dismissing such a possibility, and suggested US officials were trying to interfere.
"Maybe they did not read the rules and regulations of the commission. The Americans are expressing their views and those are not always the same as the commission's. But the commission is absolutely independent.
"It is not acceptable for anyone to interfere in our business. That will not be allowed to happen," he said.
The US has been pushing for a set number of seats for Sunni Arabs in Iraq's legislature irrespective of elections, according to The New York Times.
The US administration was talking to Iraqi leaders about guaranteeing Sunni Arabs a certain number of high-level jobs in the future Iraqi government regardless of the outcome of the 30 January election, The New York Times reported on its website.
Citing an unnamed Western diplomat, the newspaper said US officials had already raised with an aide to Ayat Allah Ali al-Sistani, Iraq's top Shia cleric, the possibility of adding some of the top vote-getters among the Sunni candidates to the 275-member legislature, even if they lose.
The diplomat said that even some Shia politicians - followers of al-Sistani - were concerned that a victory by the majority Arab Shia, effectively shutting Sunni Arabs out of power, could alienate Sunnis and lead to more internal strife, the publication said.
The paper said the idea of adding Sunnis to the legislature after the election was acknowledged by officials as likely to be difficult to carry out, but they said it might be necessary to avoid Sunni Arab estrangement.
Much of the current unrest is taking place in Sunni-dominated areas in the central part of the country, and some Sunni leaders have called for a boycott of the election.
"There is some flexibility in approaching this problem," the paper quotes an unnamed US administration official as saying.
"There's a willingness to play with the end result - not changing the numbers, but maybe guaranteeing that a certain number of seats go to Sunni areas even if their candidates did not receive a certain percentage of the vote"
Unnamed US official
"There is a willingness to play with the end result - not changing the numbers, but maybe guaranteeing that a certain number of seats go to Sunni areas even if their candidates did not receive a certain percentage of the vote."
But the report said the idea of altering election results is so sensitive that administration officials who spoke about it did not want their names revealed.
Some experts on Iraq say such talk could undercut efforts to drum up support for voting in Sunni areas, the paper pointed out.