US President Donald Trump has reportedly thrown out the existing plans drawn up under his predecessor Barack Obama on how to oust Isis from their de facto capital of Raqqa in Syria.

A detailed roadmap on how to proceed in the conflict, which is expected to be a gruelling fight lasting several months, was handed over to the new administration when Mr Trump took office last month, The Washington Post reported.

However, the plans were dismissed by Mr Trump’s team, which worried the framework was “poor staff work” with “huge information gaps” and no “plan B.”

It was also dissatisfied that the possibility of working with Russia and Turkey, two other major proxy players in Syria’s complex war, was not adequately addressed.

The report was too “incremental and risk-averse,” the new administration allegedly found. The Washington Post noted that Mr Obama’s plan, which was worked on for the better part of a year, contained advisories on minimising civilian casualties and troop numbers.

It advocated providing further training and arms for the mostly Kurdish Syrian Democratic Forces (SDF), which are currently making gains on the city.

The new president said on the campaign trail he would defeat Isis “quickly” after taking office, in the past referencing a “top secret plan”.

Donald Trump ‘open to working with Moscow’ to fight Isis in Syria

Last week it emerged that Mr Trump’s administration had asked the US military’s chiefs of staff to draw up new strategies for defeating the group, as well as the possibility of establishing safe zones for civilians in Syria.

A senior official who served in the Obama administration countered the Trump team’s criticism, telling the post that the the former president had been well aware of his plan’s shortcomings, and that further arming the Kurds was a ‘plan B’ option after it became clear Turkish forces could not be used to carry out the operation.

Meanwhile, in Raqqa, US-led coalition aircraft destroyed the main water pipeline supplying the city, as well as two bridges, amid heavy fighting on Friday, the Associated Press reported.