Washington has refused to acknowledge the Islamist organisation's strong showing, recognising only that an unprecedented number of "independents" had won despite widespread violence and intimidation.
But a senior State Department official suggested on Thursday that US officials might be in touch with victorious members of the Muslim Brotherhood, which has emerged as a key player in Egyptian politics even if it is not a formal party.
"I would expect us to meet with the independent candidates," said the official, who spoke to reporters on condition of anonymity.
The 77-year-old Brotherhood, which has renounced past ties to violence and is tolerated in Egypt, shocked Cairo by taking 88 of 444 parliamentary seats at stake in the month-long elections that wound up on Wednesday.
The Brotherhood has won 88 of
the 444 parliamentary seats
Adam Ereli, a spokesman for the US State Department, said that America would respect Egyptian law prohibiting contacts with the Muslim Brotherhood as an organisation.
But he stressed that the victorious Brotherhood candidates had been elected as independents. Asked if Washington would deal with them, he said: "There's no injunction that I'm aware of that would prevent that."
The growing political clout of Islamic hardliners has put Washington in something of a quandary, caught between supporting democratic processes and a refusal to have dealings with groups linked to violence.
The problem has been particularly sharp with organisations such as Hizb Allah in Lebanon and Hamas in the Palestinian territories, which have both scored well on the political front despite being labelled as terrorists by the US.
Without mentioning the Muslim Brotherhood, Ereli hailed the Egyptian elections as producing an "historic" broadening of opposition and independent representation in the parliament of Washington's key Middle East ally.
"We think that that's going to have a substantial impact on political life in Egypt. And that's positive," Ereli said. "That's a sign that pluralism and democracy has taken a step forward in Egypt."
But he renewed criticism of the elections as flawed, with "numerous and widespread incidents of violence, harassment and intimidation", including the death of eight people.
"So, clearly, there is cause for concern," he said. "It is an issue that we have and will continue to raise with the government of Egypt at the highest level."