Justice Secretary Michael Matheson said the delay was "disappointing". Michael Matheson said it would allow more time to engage with the Transport Police Federation on issues such as pay and conditions. The Scottish Government have rejected suggestions that this could mean a delay of up to two years.
Police Scotland's Deputy Chief Constable Iain Livingtsone said unresolved issues in the integration plan meant it could not be be achieved by the April 2019 date "without compromising public safety".
The move follows constant criticism of the merger which led former Scotland Office minister, Lord Foulkes, arguing it would "jeopardise an effective fight against terrorism". BTP officers have also spoken out against them.
The Conservatives Justice spokesman, Liam Kerr, said:
"While this SNP merger may have hit the buffers, it's time it was derailed altogether.
"The Scottish Conservatives have campaigned to stop this flawed plan for some time, and we're glad there's at least been a delay which might allow the SNP to do some proper planning and strategising.
"It's an unpopular move that virtually nobody is in favour of, with ideology and dogma seemingly the motive."
The British Transport Police Federation's chairman, Nigel Goodband, said:
"We now hope to see a realistic timeframe being set which allows for better planning, greater analysis of the costs of integration, and deeper understanding of the risks.
"The process to date has caused unnecessary worry and concern so we welcome the commitment to improving staff engagement and will continue to support this in any way we can."
In December last year, a report from Scotland's Police watchdog said no authoritative business case was made for the merger of British Transport Police and Police Scotland.
HM Inspectorate of Constabulary's overview of BTP said the decision was made by ministers, meaning the benefits, disadvantages and costs were not explained.