West Germany's balance of payments deficit swelled to $3.53 billion in April, largely because of a narrower trade surplus, the central bank reported yesterday.

The report, released by the Deutsche Bundesbank, confirmed a trend toward wider deficits in one of Western Europe's major trading nations.

West Germany's balance of payments deficit for March stood at about $2.2 billion, the band added.

In the first four months of 1980, West Germany's balance of payments has posted a deficit of about $9.84 billion, compared with a deficit of about $5.83 billion for the same period last year.

The Bundesbank said the April balance of payments deficit was due in large measure to a narrowing of the April trade surplus, which fell to $618 billion from $1.13 billion in March.

Also expanding the overall April payments balance deficit was an estimate by the Bundesbank that $2.26 billion in export credits were made available during the month.

Capital transactions tended toward balance on both the short- and long-term capital accounts, Bundesbank noted. The long-term capital account posted a deficit of $67.23 million, compared to a surplus of $1.28 billion in April.