LONDON, Sept 23 (Reuters) - London-based gold miner Randgold RRS.L has submitted its formal takeover offer to the board of Ashanti, stepping up a bidding battle against rival AngloGold ANGJ.J , sources familiar with the deal said on Tuesday.

One source said the offer was pitched at the same value as Randgold's indicative offer, which it made in August. At that time, Randgold said it would issue one of its shares for every two Ashanti AGC.GH shares, valuing Ashanti at $1.46 billion.

The Randgold offer trumped a rival bid from South African mining giant AngloGold, worth some $1.1 billion.

Randgold has timed its offer to come during the 2003 Denver Gold Forum, a gathering of the world's most senior precious metal executives, which is taking place this week.

Mark Bristow, Randgold's chief executive, is expected to use the forum to flesh out details of his company's offer during a presentation on Tuesday.

His comments will coincide with a rival presentation from AngloGold, which plans to update investors on its offer the same day.

The sources said Randgold's long-awaited offer was sent to the board of Ashanti on Tuesday afternoon and that Randgold would release an official statement later on Tuesday.

Investors have so far been lukewarm to Randgold's indicative proposal due to the company's size -- it is half the size of Ashanti -- and what they say is its limited experience and small cash pile.

AngloGold, by contrast, is the world's No. 2 gold miner and has said it would stump up almost $700 million to develop Ghana's massive Obuasi gold mining operation.

Bristow has argued that it will take at least a decade before Obuasi is fully developed and that Randgold will be able to finance the operation over that time, despite only having $100 million in cash presently.

He will also point to the far larger stake the Ghana government will retain in a combined Randgold/Ashanti. That stake will be greatly reduced if AngloGold wins out.