Malaysian lawmakers observed a moment of silence as the country marked the second anniversary of the missing of the Boeing 777, which disappeared on March 8, 2014, en route from Kuala Lumpur to Beijing with 239 people on board, Xinhua reported.
A joint search effort in the southern Indian Ocean, where the plane presumably ended its journey, has yet to reveal its whereabouts after covering 75 percent of the 120,000 square km search area.
The search is expected to be completed later this year. Najib said his country was hopeful that the plane could be found in the search area.
"The disappearance of MH370 was without precedent, and the search has been the most challenging in aviation history," Najib said in a statement.
"Amidst some of the world's most inhospitable terrain -- at depths of up to six kms, across underwater mountain ranges, and in the world's fastest currents -- the search team has been working tirelessly to find MH370's resting place," he said.
Malaysia, Australia and China will hold a tripartite meeting to determine the next step if the current search fails, said the prime minister. Most of the pasengers aboard the flight were Chinese.
Australia's Minister for Infrastructure and Transport Darren Chester on Tuesday said that authorities were committed to searching the Boeing 777 and desperately trying to solve the mystery that has baffled the world.
Although two years have passed since the flight went missing, Australia has not "forgotten" its responsibility to the victims' loved ones, Chester said.
"Finding the aircraft would give answers to the world, in particular the families of missing people, about what happened," he said.
The only confirmed debris from MH370 so far was a wing part called flaperon discovered in the French overseas Reunion Island in the Indian Ocean last year.
Malaysian and Australian authorities were verifying two more suspected pieces of debris, found in the Reunion Island and nearby African country of Mozambique respectively in the past week.