State TV ERT said the reshuffle was "hours away".
According to reports, Tsipras was expected to oust a pair of hardliners opposed to privatisations, bring in younger party members loyal to him personally, and create a separate ministry to tackle Greece's migration crisis.
But the key posts of foreign affairs, defence and finance were likely to remain unchanged.
After only a year into a four-year term, Tsipras has seen his popularity wane following a new round of tax hikes and pension cuts.
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Tsipras hopes the economy will rebound from recession this year, and has pinned his hopes on the promise of debt relief from Greece's international creditors.
Greece's central banker Yannis Stournaras has warned that the country will not be able to return to credit markets in 2018 without assurances that its debt is seen to be viable.
Yesterday, Stournaras again said "urgent action" was needed to specify what form the debt relief will take to reassure markets.
Germany opposes debt relief as unnecessary, but tackling the problem is a firm demand of the International Monetary Fund.
Tsipras' leftist Syriza party trails the conservative New Democracy party by up to 10 points in recent opinion polls.
The 42-year-old leader was elected in 2015 on his pledge to tear up Greece's austerity agreements.
He won a popular referendum on the issue but within weeks was forced to compromise with the country's international creditors and signed onto another multi-billion-euro bailout containing additional fiscal cuts.
Tsipras then dissolved parliament and called for fresh elections which comfortably returned him to power until 2019.