Recent matches between the two League One clubs have been dogged by disorder involving rival supporters.

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But the Metropolitan Police says it will be pulling out all the stops to try to prevent any repeat at tomorrow's fixture.
It will have around 400 officers providing a "robust, high-visibility presence" in and around Millwall's New Den ground.

They will include a number of so-called 'spotters' who will attempt to pinpoint known troublemakers.

The Met's Supt Peter Vincent said: "Our message to those attending is simple.

"If you're coming to enjoy the game safely and legally, we will endeavour to help you do that.

"However, if you intend to cause trouble you will find your efforts thwarted."

Special arrangements are also being put in place for the return fixture at Elland Road next Thursday.

Away fans have been given vouchers rather than the tickets they will need to gain entry to the ground.

They will have to swap their vouchers for match tickets at a motorway service station ahead of kick-off.

Leeds and Millwall have made just 1,000 tickets available to travelling fans for each game following consultations with police.

That decision was greeted with dismay by the Leeds United Supporters' Trust and its Millwall counterpart.

They fear the cap could see some away fans trying to obtain seats in home sections of Elland Road or the New Den.

The winner of the tie will face either MK Dons or Scunthorpe United in a promotion-deciding final at Wembley.

Millwall's visit to Elland Road in October 2007 was marred by repeated clashes between troublemakers and police, with travelling supporters causing thousands of pounds worth of damage to buses as they headed to the ground.

The London club's most recent game at Leeds was in February this year and passed off without incident.