The US government's deadline to raise the $31.4 trillion debt ceiling could be sooner than expected, raising the prospect of a short-term debt limit extension, analysts said on Tuesday. Goldman Sachs analysts said weak tax collections so far in April indicate a higher probability that the so-called "X-date," when the government is no longer able to pay all its bills, would be reached in the first half of June. Analysts at Citi said they expected a short-term deal in June or July.