It had offered the increase on condition the union called off the strike. "Consequently for failure to call off the strike, the government has now rescinded this offer and there will be no further negotiations," it said in a statement

Doctors were expected to "resume duty ...with immediate effect".

The strike, which began in December, has provoked anger among Kenyans and put pressure on President Uhuru Kenyatta's government ahead an election in August.

The doctors' union, which has about 5,000 members, wants the government to implement a deal agreed in 2013 to give them a 150 to 180 percent pay rise.

That agreement also called for a review of working conditions, job structures and criteria for promotions and address under-staffing in state hospitals.

The lengthy stand off between the doctors and the government has seen some union officials serve short jail terms after being found guilty of contempt of court in relation to the strike.

Opposition leader, Raila Odinga, has blamed the government for failing to resolve the pay disagreement.

The statement, jointly issued by both the central and local governments, accused the doctors of refusing to heed a court order that declared the strike illegal and of impeding efforts by various mediators to resolve the impasse.

"Due to the hard-line position of the union, which position has not moved an iota since last year, all these efforts have failed," the statement added.

One union official, Mwachonda Chibanzu, told Reuters they had no immediate comment on the order for them to resume work.