The Congressional Budget Office on Wednesday said the U.S. Treasury Department will exhaust its ability to pay all its bills sometime between July and September, unless the current $31.4 trillion cap on borrowing is raised or suspended.

In a report issued alongside its annual budget outlook, the non-partisan CBO cautioned that a historic federal debt default could occur before July if revenue flowing into the Treasury in April — when most Americans typically submit annual income tax filings — lags expectations.

The pace of incoming revenue, coupled with the performance of the U.S. economy in coming months, makes it difficult for government officials to predict the exact "X-date," when the Treasury could begin to default on many debt payments without action by Congress.