WASHINGTON -- Moderate Democrats working to gather support from Republicans for comprehensive immigration reform sent an ultimatum Friday to Speaker John Boehner: introduce a bill by Sept. 30 or they'll introduce their own.

"[W]e are frustrated that there was not a bipartisan immigration reform bill introduced prior to the August recess," reads the letter from 39 members of the New Democrat Coalition, a 53-member group, including co-chairmen Reps. Joaquín Castro (D-Texas) and Jared Polis (D-Colo.).

"Therefore, we write to inform you that if a bipartisan immigration reform package is not introduced in the House of Representatives -- one that includes a pathway to citizenship, helps grow American jobs, and fixes our immigration system once and for all -- by September 30th, we as New Democrats will consider introducing a comprehensive immigration reform bill," the letter continues. Read the letter here.

Boehner, an Ohio Republican, has said he will not bring up any immigration bill -- particularly the one that passed the Senate in June -- unless a majority of House Republicans support it. Democrats and pro-reform activists think they could get the 218 votes needed for passage of comprehensive immigration reform, if Boehner would allow for a vote, by keeping most Democrats and winning over some Republicans.

Members of Congress leave town Friday for the August recess, a month-long break during which they will hear from constituents. Meanwhile, the clock is ticking closer to primaries and the 2014 election year.

Democrats have said immigration reform should include a path to citizenship for undocumented immigrants, but many Republicans have said it's a no-go. Instead, House Republicans are pursuing a number of smaller bills, such as border security legislation. Majority Leader Eric Cantor (R-Va.) and Judiciary Committee Chairman Bob Goodlatte (R-Va.) are working on a bill to legalize undocumented young people who came to the U.S. as children, but there aren't GOP-led efforts to deal with their parents. A seven-member bipartisan group in the House is working on comprehensive legislation with a path to citizenship, though it has not yet come to a final agreement on legislative language.

The New Democrat Coalition letter says Boehner "can rely on" its members for support if he brings up a bill with a path to citizenship for undocumented immigrants.

“We have the support of the American people," it concludes. "We hope we can count on your support."

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  • The Numbers

    The House has 233 Republicans and 200 Democrats. Each party should pick up one more seat when two vacancies are filled. Going into the election, the GOP edge was 242-193. Senate Democrats will have a caucus of 55, including two independents, Angus King of Maine and Bernie Sanders of Vermont. Republicans have 45. That's a pickup of two seats for Democrats. <em>(Text <a href="http://www.huffingtonpost.com/huff-wires/20130103/us-new-congress-glance/">via the Associated Press</a>)</em>

  • Women

    The House will have 79 women, including 60 Democrats. At the end of the last session, there were 50 Democratic women and 24 Republican women. The new Senate will have 20 women members, an increase of three. That consists of 16 Democrats and four Republicans. The last Senate had 12 Democratic women and five Republicans. (Text <a href="http://www.huffingtonpost.com/huff-wires/20130103/us-new-congress-glance/">via the Associated Press</a>)

  • Freshmen

    With two vacancies to be filled, the House has 82 freshmen; 47 Democrats and 35 Republicans. As of the end of the last session, 87 of 103 freshmen were Republicans. The Senate will include 14 new faces, with nine Democrats and the independent King. Five are women. New senators include Brian Schatz, who was sworn in on Dec. 27 to fill the seat of the late Hawaii Democrat Daniel Inouye. (Text <a href="http://www.huffingtonpost.com/huff-wires/20130103/us-new-congress-glance/">via the Associated Press</a>) <em>(Pictured at left: Incoming House freshmen of the 113th Congress pose for a group photo on the East steps of the Capitol in Washington, Thursday, Nov. 15, 2012. AP Photo/Susan Walsh)</em>

  • African Americans

    The House will have 40 African-Americans, all Democrats. The number of Democrats is unchanged, although two Republicans will be gone: Allen West, R-Fla., lost his re-election bid, and Tim Scott, R-S.C., was appointed to fill the Senate seat of Jim DeMint, R-S.C., who is retiring. Scott will be the first black lawmaker in the Senate since Roland Burris, who retired in 2010 after filling the Illinois Senate seat of Barack Obama for almost two years. (Text <a href="http://www.huffingtonpost.com/huff-wires/20130103/us-new-congress-glance/">via the Associated Press</a>) <em>(Pictured at left: Rep. Tim Scott, R-S.C., who was appointed by South Carolina Gov. Nikki Haley to replace outgoing Sen. Jim DeMint, R-S.C., walks out of the Republican policy luncheon on Capitol Hill in Washington, Tuesday, Dec. 18, 2012. AP Photo/Susan Walsh)</em>

  • Hispanics

    The new House will have 33 Hispanics, with 25 Democrats and eight Republicans. That's up slightly from last year. The Senate will have three Hispanics: Democrat Robert Menendez of New Jersey, Republican Marco Rubio of Florida and Republican freshman Ted Cruz of Texas. (Text <a href="http://www.huffingtonpost.com/huff-wires/20130103/us-new-congress-glance/">via the Associated Press</a>) <em>(Pictured at left: Rep.-elect Joaquin Castro, D-Texas, speaks with members of the media after a news conference with newly elected Democratic House members on Capitol Hill in Washington, Tuesday, Nov. 13, 2012. AP Photo/Pablo Martinez Monsivais)</em>

  • Other Minorities

    The new House will have nine Asian Americans, all Democrats. There are two American Indians: Tom Cole, R-Okla., and Ben Lujan, D-N.M. (Text <a href="http://www.huffingtonpost.com/huff-wires/20130103/us-new-congress-glance/">via the Associated Press</a>) <em>(Pictured at left: Sen.-elect, current Rep. Mazie Hirono, D-Hawaii, and her husband, Leighton Oshima ride the Senate Subway on Capitol Hill in Washington, Tuesday, Nov. 13, 2012. AP Photo/Harry Hamburg)</em>

  • Other Facts

    According to CQ Roll Call newspaper, the average age of House members in the 113th Congress is 57; the average age of senators is 62. It estimates that the House will include some 277 Protestants and Catholics, 22 Jews, two Muslims and two Buddhists. The Senate will have 80 Protestants and Catholics and 10 Jews. The House will have its first Hindu, Rep.Tulsi Gabbard, D-Hawaii. Senate freshman Mazie Hirono, also of Hawaii, will be the Senate's only Buddhist and its first Asian American woman. Also for the first time, white men will be a minority among House Democrats. (Text <a href="http://www.huffingtonpost.com/huff-wires/20130103/us-new-congress-glance/">via the Associated Press</a>) <em>Pictured at left: Rep.-elect Tulsi Gabbard, D-Hawaii is seen on stage during a news conference with newly elected Democratic House members, on Capitol Hill in Washington, Tuesday, Nov. 13, 2012. AP Photo/Pablo Martinez Monsivais)</em>