A deep-pocketed anonymous donor has stepped forward with a $20 million donation that could allow Lincoln Square Synagogue to continue building its new shul.

The synagogue announced the gift at a special meeting Thursday night.

Lincoln Square Synagogue halted work last month on its new building at 180 Amsterdam Ave. — the first new synagogue to be built in Manhattan in 50 years — because it didn’t have enough money to cover ballooning construction costs.

Now the hammers could start swinging again.

The anonymous donation is contingent upon the synagogue raising $3 million on its own by April 30. Synagogue leaders said in a statement that they’re hoping every member of the congregation will pitch in on the fundraising effort.

“We are exhilarated by this vote of confidence in the future of our synagogue and humbled by the size and generosity of the donation,” Rabbi Shaul Robinson, senior rabbi at the synagogue, said in a statement. “We thank God for having sent this extraordinary gift our way.”

The synagogue has had several prominent members over the years, including Supreme Court Justice Elena Kagan, who was the first girl to celebrate a bat mitzvah at the synagogue.

Other well-known members include Sanford Bernstein, the founder of the investment firm Sanford C. Bernstein & Co., and Paul Shaffer, the bandleader on “The Late Show with David Letterman.”

Lincoln Square Synagogue broke ground on its new building in 2007 and hoped to finish within 18 months. (DNAinfo/Leslie Albrecht)

Lincoln Square Synagogue’s new building was initially expected to cost roughly $19 million, but construction costs have skyrocketed and another $15 to $20 million is needed to complete the project.

Lincoln Square Synagogue began in an apartment in Lincoln Towers in 1964. Its current building at Amsterdam Avenue and West 69th Street was built in 1971. In the 1980’s it bought a nearby bank building and now uses both structures for a variety of classes and groups.

A developer paid the synagogue $19 million for the two buildings, which the developer wants to replace with a high-rise. Originally that money was supposed to cover the cost of the new synagogue.

(Source: DNA Info)