Secretary of State William F. Galvin, said today that the special election to fill John F. Kerry’s Senate seat will take place June 25, with a primary set for April 30.

Galvin said his decision about the date was based on a conversation with the secretary of the Senate in Washington. Galvin recommended the June 25 date to Governor Deval Patrick, who has the final say, and is expected to sign off on it.

Kerry, who breezed through a confirmation hearing before the Senate Foreign Relations Committee last week, is expected to submit his resignation Tuesday just before the full Senate votes on his nomination.

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Galvin said he will make Senate nomination papers available as quickly as possible this week. Candidates have four weeks to gather 10,000 certified voter signatures for their names to appear on their party’s primary ballot.

“It’s going to be a momentous week,’’ Galvin said. “Once we set the date, the race is on.”

On the Democratic side, US Representative Edward J. Markey is the only candidate to have formally declared. His colleague Representative Stephen F. Lynch is expected to make a decision whether to run this week. The Republicans have yet to have a candidate emerge. Former senator Scott Brown has not indicated whether he will seek to get back into the Senate.

The law mandates that the special election be held between 145 and 160 days after a vacancy occurs.

Governor Deval Patrick said at a news conference today that he expects to appoint an interim senator on Wednesday. That person will fill the seat until the special election is held.