Drilling services and mining contractor Ausdrill is considering issuing $US300 million in unsecured notes to USA-based institutional investors.

Ausdrill said today that its wholly-owned subsidiary Ausdrill Finance may potentially issue the notes, to repay outstanding debts under its $550 million debt facility announced early this month.

Upon repayment, $US250 million of Ausdrill's commitments under the facility would be cancelled.

At close of trade today, Ausdrill shares were down 2.6 per cent, trading at $2.92.

Ausdrill announced its $550 million finance facility earlier this month, which it said would allow it to refinance existing debts and fund the acquisition of Best Tractor Parts.