The United States says it is "disappointed" with the way Egypt conducted its parliamentary elections on Sunday.
White House National Security Council spokesman Mike Hammer says the United States is assessing reports of problems that include polling irregularities, a lack of international monitors and, as he put it, "the many problems encountered by domestic monitors."
In a Tuesday statement, he calls the reports "worrying."
Preliminary results indicate a sweeping victory for the ruling National Democratic Party. However, opposition groups say the voting was unfair. Official results are expected later Tuesday.
The opposition Muslim Brotherhood, which won one-fifth of seats in 2005 elections, says none of its candidates won seats in Sunday's first round of voting.
However, in a Tuesday statement, it says more than 20 of its candidates will compete in a December 5 runoff. Also, Deputy Chairman Mahmoud Ezzat said the party would not refrain from helping Egyptian citizens even if its party members do not get into parliament.
The Muslim Brotherhood is illegal in Egypt, which bars religious parties. So, the group's candidates run as independents.
On Monday, protesters clashed with police across the country after the group said a "rigged" election had virtually wiped out its presence in parliament. Three people were reported killed in the violence
Voters, opposition campaigners and a coalition of local and international rights groups reported systematic rigging, bribery and other election-day infringements after the government prevented monitoring.
The run-up to the vote was also dogged by charges of harassment and intimidation. Several hundred Muslim Brotherhood members were arrested in the latest in a series of crackdowns on the group.
Although the government promised a free and fair election, it barred international monitors, calling them an infringement of its sovereignty.
Egypt is scheduled to hold a presidential election next year. Mr. Mubarak, who is 82 and has been president since 1981, has not said whether he will run for re-election.
Some information for this report was provided by AP, AFP and Reuters.