LONDON—The European Union cannot decide yet on granting Britain access to the bloc’s financial market, even though London and Brussels have agreed a trade deal, a European Commission official said on Thursday. While the landmark trade deal agreed on Thursday set rules for industries such as fishing and agriculture, it did not cover Britain’s much larger and influential finance sector. There were hopes the trade deal would pave the way for more access to the EU for Britain’s finance industry, but the EU indicated it was in no rush to grant it. Brussels has only granted financial market access, known as “equivalence,” for two financial activities from Jan. 1, when Britain will have left the EU’s single market. The Bank of England has said there could be disruption in markets if no further access is allowed. Just minutes after Britain and the EU hailed their agreement on trade, the bloc’s …