A US House of Representatives committee has voted along party lines to hold Attorney General Eric Holder in contempt of Congress.
Mr Holder refused to hand over papers relating to a botched sting operation.
The move comes after President Barack Obama used his executive privilege to withhold documents sought by the House Oversight Committee.
But Mr Holder said claims he did not co-operate over Operation Fast and Furious were “untrue”.
The operation at the centre of the row saw US agents lose hundreds of illegal guns let into Mexico to trace arms dealers.
US border agent Brian Terry was killed in December 2010 in a shootout with illegal immigrants with a weapon linked to Fast and Furious.
The congressional investigation was opened after two guns retrieved at the scene were found to be among 2,000 weapons authorities were supposed to be tracking.
By Al Arabiya with agencies
The body overseeing Egypt’s presidential election said it would not announce the results on Thursday as planned, saying it needed more time to study appeals from the candidates, but did not say when it might be ready, the state news agency reported.
The Egyptian presidential run-off pitted the Muslim Brotherhood’s Mohamed Mursi against Ahmed Shafik, a former air force commander who was Hosni Mubarak’s last prime minister. Both claim to have won and have filed appeals against each other.
“The (election) committee has decided to continue to examine the appeals, which involves looking at records and logs related to the electoral process, and this will necessitate more time before announcing the final results,” it said in a statement on Wednesday.
Earlier, Committee Secretary-General Hatem Bagato told Reuters he could not say when the results would be announced.
“We are at the stage of listening to the representatives,” he said.
“The committee will meet afterwards to decide on whether to accept the appeals or not. After that, there will be a time set to announce the final result,” he added, speaking by phone.
On Tuesday, a U.S. election monitoring group said it was unable to say if Egypt’s presidential election was free and fair as it had not been given sufficient access, accusing the military leadership of hampering a transition to democracy.
Beyond the election itself, the group – the Carter Center – said a court’s decision to dissolve the Islamist-dominated parliament and a decree from the ruling military council limiting the future president’s powers increased the risk that Egypt was not becoming the democracy that many had hoped for.