"admittedly challenging" is correct and can be used in written English.
You can use it when admitting that something is difficult to do or accomplish. For example, "Running a marathon is admittedly challenging, but it can be done with determination and proper training."
Certain scenes – such as the admittedly challenging one in which Queen Tamora (a vixenish Ivy Pang Ngan-ling) attempts to impersonate the goddess of revenge – failed to come off at all.
It is admittedly challenging to identify satisfactory control groups for area based interventions.
"In an admittedly challenging time, this merger provides the ideal combination of established journalism authority and bright, bristling website savvy," Mr Harman said.
In particular, designing an efficient query processing scheme is admittedly challenging in mobile ad hoc networks (MANETs) because of the lack of centralized coordination, limited computing and communication capabilities, and time-varying network topologies.
These are admittedly challenging experiments, but without them the current study does not resolve the current controversy over where and when capsid uncoating occurs.
While it is clear that Malaysia has achieved significant and commendable progress in providing children with access to education – it is also clear more must be done to pursue the admittedly challenging goal of also ensuring access for the poor, marginalised and the excluded to education.
These generalizations admittedly are challenged by many exceptions but the electoral maps attest that the blue (Democratic) clusters are in cities and the Republican support is strongest in the vast lands of rural America.
What Bob surely thought was an attractive point of pride, living a pedestrian and cyclist lifestyle in a car-centric city, was challenging my admittedly conventional dating expectations.
As the author of an optimistic green book who's admittedly felt somewhat challenged since the BP spill, I've been invited to speak to a Surfrider Foundation Hawaii chapter about simple ways we can help protect the seas in our daily lives.
The inferences drawn from these observations admittedly could be challenged given the limitations of a nonrandomized, observational study, and they suggest that further prospective evaluations are warranted.
He's an anti-hero with whom 21st-century souls can identify, though admittedly our challenge as we commemorate the centenary of the start of the first world war, is to imagine what it was like to be otherwise – to believe literally in what Wilfred Owen called the old Lie: Dulce et Decorum est/ Pro patria mori.
