Kohlberg Kravis Roberts, the best-known name in leveraged buyouts, pressed the button on its long-awaited flotation in the United States last night in a deal expected to value the firm at up to $15 billion (£7.5 billion).

KKR, whose record $31 billion takeover of RJR Nabisco was captured in the bestselling Barbarians at the Gate, owns Alliance Boots, the chemist chain that was the focus of Europe's biggest buyout in an £11 billion takeover last year. It also owns TXU, the power utility, and First Data, the credit card issuer.

The firm will be listed on the New York Stock Exchange through a two-part transaction under which it will buy out KKR Private Equity Investors, the investment fund that it floated on Euronext Amsterdam two years ago. Through a stock swap, shareholders in the fund will own 21 per cent of the new and enlarged entity, while shareholders in the privately held KKR will receive the remaining 79 per cent.

The fallout from the credit crunch has pushed shares in KKR Private Equity Investors down from their $25 issue price to about $10. Through a flotation in New York as part of a larger and more liquid company, KKR hopes that the fund will be able to close the discount to its estimated $22 billion net asset value. The step should also enable KKR to draw a line under a flotation that has proved a persistent source of frustration to both Henry Kravis, the firm's co-founder and managing partner, and its shareholders.

KKR initially filed a registration statement to list in New York as a standalone company in July 2007 with an intention to raise $1.25 billion. Those plans were derailed by the collapse in debt markets that began last summer. In its revised form, KKR will not raised any fresh capital - unlike Blackstone Group, its arch rival, which last year secured $4 billion in the last month before the credit crunch stuck.

Speculation that KKR would dust off its flotation plans has resurfaced in recent weeks after a string of hirings and internal appointments that have given it an additional tier of management that more closely resembles that of a public company. It has reassigned Todd Fisher, previously one of its leading dealmakers in London, to the role of chief administrative officer and has brought in a general counsel and a chief technology officer, among others.

The float will also inevitably stoke suggestions that Mr Kravis and George Roberts, the firm's other remaining co-founder, are preparing for their eventual exit. Publicly traded stock will provide currency to incentivise their successors and also enable them to monetise their investments. The pair, both 64, remain the largest shareholders in the company.

So far this year, KKR has not struck a single buyout deal in America. Its most high-profile transaction has been a financial services investment - a $1.25 billion stake in Legg Mason, the US fund manager. However, shares in Legg Mason have fallen by about 45per cent since KKR bought into it.

KKR has also diversified into investing in infrastructure, a further move away from the big-ticket buyouts with which it made its name, as well as into property.

Analysts expect the flotation to increase pressure on other leveraged buyout firms to float, given the advantage that it will give KKR in access to capital. Carlyle Group and TPG are seen as the most likely candidates to follow suit. However, there is an irony that KKR is pursuing a flotation at what is recognised as the greatest period of turmoil in buyout markets for decades.

The procedural complexities involved in buying out the European fund mean the flotation is not expected until the fourth quarter of this year.

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