By David Morgan

WASHINGTON A group of hardline Republicans has put new U.S. House Speaker Mike Johnson on notice that he can no longer count on their support for legislation, signaling a possible early end to his "honeymoon" period.

Three weeks after the Louisiana lawmaker won the gavel of the House of Representatives, 19 House Republicans - including 15 hardliners - voted to block debate on their party's bill to fund federal programs on commerce, justice and science for fiscal 2024, which began on Oct 1.

"We want the message to be clear," said Representative Scott Perry, chairman of the hardline conservative House Freedom Caucus. "We're not going to pass bills that don't address the problems that America faces."

It was the second floor protest this year by Freedom Caucus members and others, who were angered by Johnson's decision not to include spending cuts and conservative polices such as U.S.-Mexico border restrictions in his stopgap measure to avert a partial government shutdown on Saturday.

"The honeymoon is probably over," said Representative Nick LaLota, one of four Republicans from New York swing districts who also opposed opening debate on Wednesday because of abortion restrictions and law enforcement spending cuts in the underlying legislation.

Johnson's office did not respond to a request for comment.

Some hardliners who opposed Johnson on Wednesday also shut down the House floor in June to protest against a 2024 spending deal between President Joe Biden and then-House Speaker Kevin McCarthy, who was forced to adjourn the chamber days early.

McCarthy was ousted by eight hardliners on Oct. 3, after averting an Oct. 1 shutdown with a stopgap bill that ran afoul of the far right but won overwhelming support from Democrats.

Johnson, who has commanded respect within the far right as an outspoken Christian conservative, irked hardliners this week with his own short-term spending bill to maintain existing government funding levels and programs into early 2024.

The bill passed the House with support from 209 Democrats but only 127 Republicans - a troubling sign for the new speaker. He had also angered hardliners by suspending House rules to circumvent their hopes of blocking debate on the measure.

The Senate passed the bill late on Wednesday.

The House has passed seven 2024 appropriations bills, all of them partisan Republican measures that are unlikely to become law.

But Republicans have been unable to agree on their remaining five spending bills.

Hardliners now want Johnson to marshal his fractious 221-213 Republican majority into agreement on spending and then fight the Democratic-led Senate for spending cuts and policy changes that would defund programs that Democrats view as priorities.

"We like him a lot. He's a nice guy," hardline Representative Anna Paulina Luna said of Johnson. "But we're going to make sure that he follows through on what he said he was going to do."

(Reporting by David Morgan; Editing by Scott Malone and Deepa Babington)