Law and Parliamentary Affairs Minister TB Jayachandra told reporters that a copy of the ordinance would be sent to Governor Vajubhai Rudabhai Vala tomorrow for assent.
The proposed amendment to the 'Karnataka Determination of Seniority of Government Servants Promoted on the Basis of Reservation Act 2002' is seen as an escape route to the February 9 Supreme Court verdict that had struck down reservation in promotions for SC/ST employees.
Asked whether there could be any legal hurdle challenging the ordinance, the minister said, "Let us wait and watch."
Before taking the decision, Mr Jayachandra said the cabinet panel had held detailed discussions on a report submitted by the Additional Chief Secretary Rathna Prabha on the issue.
"Thereafter, the state law department drafted a bill to provide reservation for SC/ST employees," he added.
The court had held that Karnataka must demonstrate backwardness, inadequacy of representation and maintenance of efficiency before providing reservation in promotions, he said.
It had given three months' time to review the seniority list and another three months to appraise it of the need for consequential reservation for SC/ST employees, Mr Jayachandra said.
The cabinet decision is seen as an attempt by Chief Minister Siddaramaiah to preserve the Dalit vote bank in the run up to next year's assembly elections.
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.