(Repeats Oct. 1 column with no changes to text. John Kemp is a Reuters market analyst. The views expressed are his own)

* Chartbook: tmsnrt.rs/2OvBJTE

LONDON, Oct 1 (Reuters) - Hedge fund managers are increasingly betting Saudi Arabia and its allies cannot or will not replace all the crude lost from the market when U.S. sanctions on Iran go into effect fully from November.

Hedge funds and other money managers increased their combined net long position in the six major petroleum contracts by another 50 million barrels in the week to Sept. 25.

Portfolio managers have raised their combined net long position by a total of 196 million barrels over the last five weeks, according to exchange and regulatory data.

Bullish long positions now outnumber bearish short ones by a ratio of more than 12:1, and the imbalance is rapidly closing in on the record 14:1 back in April.

But the new wave of hedge fund bullishness is concentrated almost entirely in Brent rather than WTI or refined fuels (tmsnrt.rs/2OvBJTE).

Fund managers have raised their net in Brent by 172 million barrels since Aug. 21 compared with an increase of just 5 million in WTI.

Fund managers now hold a net long position of almost 500 million barrels in Brent betting prices will increase even further from their current four-year high.

Hedge fund long positions outnumber short ones in Brent by more than 19:1, up from a ratio of just 8:1 at the start of August, and closing in on the record 21:1 set in April.

Traders foresee a shortage of seaborne crudes linked to Brent as U.S. sanctions on Iran go into effect on Nov. 4, despite reassurances from Saudi Arabia, Russia and the United States supplies will remain adequate.

Concern about feedstock shortages linked to sanctions explains why position-building has been overwhelmingly concentrated in Brent rather than WTI or refined fuels.

The inland U.S. crude market remains well-supplied and refined fuel markets appear balanced as an international freight slowdown and higher prices take their toll on consumption.

But Brent spot prices have climbed by more than $12 per barrel (17 percent) since mid-August while the six-month calendar spread has risen almost $2.60 and swung from contango into a pronounced backwardation.

Saudi Arabia and Russia have both pledged to increase production to make up for the loss of crude oil exports from Iran. U.S. officials have been working with refiners in Asia to find replacements or Iranian oil.

None of that has assuaged fears about shortfalls in crude availability as sanctions go into effect.

Some analysts question whether Saudi Arabia has enough spare capacity to replace all the barrels lost as a result of sanctions while maintaining enough in reserve to meet any further shortfalls.

Others question whether the kingdom is willing to increase production enough to act as a cap on prices or bring them back down below $80, despite political pressure from the United States.

The enormous concentration of hedge fund long positions in Brent creates a significant risk of a short-term price reversal if and when fund managers attempt to realise some of their profits following the rally.

For the time being, however, with doubts swirling around the outlook for oil supplies, the message from hedge fund managers is simple: show me the barrels.

Related columns:

- Oil market hears echoes of 2007/8 (Reuters, Sep. 24)

- Hedge funds bet on shortage of Brent oil (Reuters, Sep. 24)

- Traders bet Iran sanctions will leave market short of crude (Reuters, Sept. 11)