NEW YORK (REUTERS) - Mrs Hillary Clinton's campaign was worried about the "hard balance" she would need to strike as the presidential candidate prepared to oppose a Pacific trade pact championed by President Barack Obama that she once supported, according to e-mails published on Tuesday (Oct 11) by WikiLeaks.

WikiLeaks released its latest batch of apparently hacked personal e-mails of Clinton campaign chair John Podesta with exactly four weeks left in the 2016 presidential campaign before the Nov 8 election.

White House hopefuls have made trade a key theme of their campaigns, with the 12-nation Trans-Pacific Partnership (TPP) a prime target for criticism by both Democrat Clinton and Republican opponent Donald Trump.

In an Oct 6, 2015 e-mail the day after the Obama administration finalised the details of the TPP, Clinton speechwriter Dan Schwerin circulated a new draft of a statement the campaign was preparing about Mrs Clinton's position, according to WikiLeaks.

"This is indeed a hard balance to strike," Mr Schwerin wrote in the e-mail to a handful of top advisers, "since we don't want to invite mockery for being too enthusiastically opposed to a deal she once championed, or over-claiming how bad it is, since it's a very close call on the merits".

The next day, as she campaigned in Iowa, the first state to pick candidates during the nominating contest, the campaign released a statement from Mrs Clinton saying the pact did not meet the "very high" bar she had set to earn her support.

The Clinton campaign declined to verify the authenticity of the latest batch of Podesta e-mails released by WikiLeaks.

Mr Podesta told reporters on Tuesday that the Federal Bureau of Investigation notified him it is investigating the "criminal" hack of his e-mails published by WikiLeaks as part of a broader political hacking probe.

The US government last week formally accused Russia of hacking Democratic Party organisations in an effort to influence the presidential election, a charge Russia has denied.

As a result, Clinton campaign officials and supporters have warned that such e-mail releases could include fraudulent or misleading documents among genuine e-mails.

Mrs Clinton's October 2015 announcement on the TPP came just a week before the first debate in her primary race against US Senator Bernie Sanders, a vocal opponent of the deal. Key Democratic constituencies, such as progressives and organised labour, have also criticised the pact.

Mrs Clinton had previously declined to say whether she would support the TPP, a main tenet of Mr Obama's strategic pivot to Asia that began when she was his secretary of state from 2009 to 2013, explaining that she wanted to wait to assess the final negotiated terms.

"I accept the position we're taking but she has generally been more pro-trade than anti," Clinton strategist Joel Benenson responded to the draft from Mr Schwerin. "While we're opposing this, don't we want to say something generally about ensuring American manufacturers can compete around the world?"

EARLY WARREN MEETINGS

Mrs Clinton's nascent campaign began meeting advisers to US Senator Elizabeth Warren even before Mrs Clinton announced her second White House bid, according to the hacked e-mails.

In a January 2015 e-mail sent three months before Mrs Clinton officially launched her campaign, Mr Schwerin briefed close aides about a meeting with a longtime policy adviser to Ms Warren, a firebrand leader of the Democratic Party's liberal wing.

Ms Warren's team was concerned that Mrs Clinton would staff her campaign with economic advisers that were too closely associated with the centrist policies of her husband, former president Bill Clinton, such as those championed by his treasury secretary, Mr Robert Rubin.

The Warren adviser, Mr Dan Geldon, "laid out a detailed case against the Bob Rubin school of Democratic policymakers, was very critical of the Obama administration's choices", Mr Schwerin wrote.

Mr Schwerin said he and Mr Geldon went over a list of recommended hires that Ms Warren had sent to Mrs Clinton. Mr Geldon told him they would be "watching carefully" to see how Mrs Clinton staffed her campaign, Mr Schwerin wrote.

"They seem wary - and pretty convinced that the Rubin folks have the inside track with us whether we realise it yet or not," Mr Schwerin wrote of Ms Warren's advisers. Mr Geldon declined to comment on the e-mail.

Mr Schwerin also added that Mr Geldon expressed "some flexibility on Glass-Steagall", a Depression-era law that prohibited commercial banks from engaging in risky trading activities that was repealed during Mr Bill Clinton's administration. "Said too big too fail is the bigger issue," Mr Schwerin wrote.

Many Democratic activists believe that reinstating Glass-Steagall would help prevent future financial crises such as the one that rocked the US economy in 2008.

Ms Warren has said that there are two ways to break up too-big banks, either based on size alone or by instituting a modern version of Glass-Steagall. She introduced a Bill in the US Senate to reinstate a version of the law.

Mrs Clinton weighed supporting a new Glass-Steagall law but eventually rejected that route, announcing a risk-based approach for breaking up banks, according to an e-mail WikiLeaks released on Monday.