Liberal lawmakers on Thursday urged opposition to an imminent war funding measure and issued a challenge to their fiscally conservative Democratic colleagues.

“If you’re serious about fiscal responsibility, oppose the Afghanistan funding,” said Rep. John Conyers (D-Mich.), chairman of the 21-member Out of Afghanistan Caucus, which formed in May.

Out of Afghanistan Caucus members plan to request a meeting with President Barack Obama on the subject in the coming weeks, Conyers said.

House Democrats, who could vote as soon as today on Obama’s supplemental war spending request, are increasingly divided over U.S. efforts in Afghanistan.

Out of Afghanistan Members opened up a new front in their campaign Thursday when they argued that — nearly nine years after military action began in Afghanistan — it is time to stop exempting war money from pay-as-you-go budgeting rules.

The lawmakers called on fiscally conservative Democrats — who have balked at additional spending that’s not offset elsewhere — to abandon what they characterized as the “hypocrisy” of not also insisting that war funds be paid for.

“The people that have been going around and saying ‘the sky is falling’ because of the debt and the deficit, we’re asking them to put up,” said Raúl Grijalva (D-Ariz.), co-chairman of the Congressional Progressive Caucus.

Liberals are pushing two amendment votes aimed at forcing an end to U.S. military efforts in Afghanistan. Congressional Black Caucus Chairwoman Barbara Lee’s (D-Calif.) proposal would cut off funding for combat operations and require the Defense Department to immediately begin withdrawing troops, while a proposal from Rep. Jim McGovern (D-Mass.) would set a flexible timetable for troop withdrawal. War opponents have been increasingly skeptical of Obama’s plan to begin bringing troops home in July 2011.

“If the Congress allows it, this will be an endless war,” Lee said. “Enough is enough.”

House Democratic leaders are trying to accommodate a request from liberals for a separate vote on the war money so that they can vote for domestic items, such as $10 billion to stem teacher layoffs, while opposing the war money. But it’s unclear whether there would be enough support for either piece of the supplemental if there were split votes. The House also is expected to vote on Democrats’ one-year budget enforcement document, which Budget Chairman John Spratt (D-S.C.) released Thursday morning, as part of the supplemental.