Hishammuddin Hussein said underwater drone Bluefin-21 would finish searching the area within the next week.
The Bluefin 21 mini-submarine has so far found nothing after six missions.
Malaysia Airlines flight MH370 went missing on March 8 as it flew from Kuala Lumpur to Beijing carrying 239 people.
The Bluefin is mapping the area of the sea bed within 6 miles radius of where acoustic signals were detected believed to have come from the aircraft’s flight recorder.
It is operating at a depth of more than 13,000 feet.
Hishammuddin Hussein said it was important to focus on the search on Saturday and Sunday.
“The narrowing of the search for today and tomorrow is at a critical juncture,” he said.
“I appeal to everyone around the world to pray and pray hard that we find something to work on in the next couple of days.”
Using satellite data, officials have concluded that the MH370 ended its journey in seas west of the Australian city of Perth.
They do not know why the plane flew so far off course and finding the plane’s flight recorders is seen as key to understanding what happened.
The Bluefin-21, operated by the US Navy off the Australian vessel Ocean Shield, is an autonomous underwater vehicle (AUV) that can identify objects by creating a sonar map of the sea floor.
It is searching in an area defined by four acoustic signals picked up by an Australian search team, and was deployed after officials concluded that the batteries on the plane’s flight recorders would likely have expired, given their one-month shelf life.
Submersible Bluefin-21 has an operating depth of 4,500m (15,000ft) and on its first mission a built-in safety device returned it to the surface after it exceeded that depth.
The authorities have now adjusted the device to allow it to go as deep as 4,695m.
The Joint Agency Co-ordination Centre (JACC) said on Thursday that the machine could operate deeper than 4,500m at “a small but acceptable level of risk”.
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