KBR has been among firms involved in reconstruction in Iraq

Shares in KBR rose to $20.80 (�10.96), up from the initial listing price of $17 on the New York Stock Exchange.

The UK government wanted the listing to be postponed, fearing that it could threaten the UK's Devonport dockyard, which is operated by KBR.

KBR is also the subject of a US probe for alleged bribery in the 1990s.

The governmental probe involves investigations by the US Department of Justice and the US Securities and Exchange Commission.

It has also been accused on overcharging the US government in Iraq, and failing to provide adequate information, by the US auditor.

KBR said it planned to use money from the listing to pay debts to Halliburton subsidiaries amounting to some $450m (�238m).

UK concerns

The British Ministry of Defence had wanted the listing to be postponed on concerns that the Devonport dockyard - the biggest naval port in Western Europe - might be compromised by the listing.

The dockyard - the only place capable of refitting and refuelling the country's nuclear submarine fleet - is owned by Devonport Management Limited, in which KBR has a controlling 51% share.

Before the listing, the British Government said it feared that once KBR was separated from parent oil services firm Halliburton, it might not have adequate funds to run Devonport effectively.