US Army whistleblower Chelsea Manning has been jailed for a second time after refusing to provide testimony before a federal grand jury.

Manning was detained after refusing to answer questions about her 2010 public disclosures of military and diplomatic secrets before the grand jury earlier this week.

Manning can be held for the term of the grand jury and not longer than 18 months, Manning’s attorney Moira Meltzer-Cohen told reporters outside a federal courthouse in Alexandria, Virginia. Asked if Manning was prepared stay imprisoned for 18 months, Meltzer-Cohen said “we are not there yet”.

Ms Meltzer-Cohen added that it was “quite likely” they would appeal the order.

“As everybody knows, Chelsea has tremendous courage. Our primary concern at this point is her health while she is confined and we will be paying close attention,” Ms Meltzer-Cohen said.

Manning had earlier told reporters she was prepared to go to jail for not answering questions regarding her involvement with anti-secrecy website WikiLeaks.

She said she opposes the grand-jury system as a matter of principle.

It follows a judge’s decision on Tuesday (local time) to reject an effort by Manning to quash the subpoena demanding her testimony.

But Manning said after the hearing in federal court that she will continue her legal efforts to avoid testifying to the grand jury.

Afterwards Manning denounced grand juries as “terrible”, noting the rules prohibit her lawyers from accompanying her during her testimony and other rules she said bend the process to suit prosecutors’ whims.

“The idea that there is such a thing as an independent grand jury is long gone,” she said.

Prosecutors in Alexandria have long been investigating Wikileaks. Manning served seven years of a 35-year military sentence for leaking a trove of military and diplomatic documents to Wikileaks before then-President Barack Obama commuted her sentence.

Last year, prosecutors in Alexandria inadvertently disclosed that Wikileaks founder Julian Assange is facing unspecified, sealed criminal charges in the district.

Wikileaks has emerged as an important part of Special Counsel Robert Mueller’s investigation into possible Russian meddling into the 2016 presidential election, as investigators focus on whether President Donald Trump’s campaign knew Russian hackers were going to provide emails to Wikileaks stolen from Democratic organisations, including presidential candidate Hillary Clinton’s campaign.

But the Alexandria prosecutors’ investigation of Wikileaks predates 2016, so there’s no obvious link between the efforts to subpoena Manning and Wikileaks’ role in disseminating the hacked emails.

© Nine Digital Pty Ltd 2019

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