The US government risks an unprecedented default as soon as July if the debt ceiling is not raised, the Congressional Budget Office has warned amid a growing war of words between the White House and congressional Republicans over lifting the borrowing limit.

The CBO, a non-partisan government agency that analyses fiscal policy for Congress, projected on Wednesday that if the debt ceiling, the legal limit on the government’s borrowing, is unchanged, the government’s “ability to borrow using extraordinary measures will be exhausted between July and September 2023”.

The exact timing for the cliff edge is dependent in part on income tax receipts due in April. The CBO noted that if these receipts fall short of current estimates, the Treasury could “run out of funds” before July.