WASHINGTON -- Congress appears in danger of again missing a self-imposed deadline on a critical spending measure, as House and Senate negotiators struggle to reach a deal to keep federal highway and public transit programs funded beyond June 30.

House Majority Leader Eric Cantor, Virginia Republican, said he remained "hopeful" a long-term highway bill could be hammered out by the end-of-the-month deadline.

But, if not, he suggested House GOP leaders were ready to accept a temporary stop-gap funding measure to assure federal transportation projects dont screech to a halt.

"Were prepared to make sure that theres no stoppage of transportation programming and funding - all the while desiring a much-longer-term solution," he said.

House Minority Leader Nancy Pelosi, California Democrat, said another short-term extension would be "completely inappropriate." And House Minority Whip Steny H. Hoyer, Maryland Democrat, said more delay would undermine investor and international confidence in the federal government and hurt the U.S. economy.

But Rep. Pete Sessions, Texas Republican, pushed back at Democrats accusations that Republicans were obstructing progress on the bill, saying House GOP leaders, including Speaker John A. Boehner of Ohio, are ready to do what is necessary to ensure a long-term measure is passed.

In March, the Senate passed a two-year, $109 billion highway bill with wide bipartisan support. But the move to renew surface transportation funding stalled in the House, where Republicans rejected their leadership's five-year, $260 billion version before the measure could even get to the floor for a vote.

One sticking point is a Republican push to include a provision for the construction of the Keystone XL oil pipeline, which would bring oil from the tar sands of Alberta, Canada, to the Gulf Coast. It has strong support from business and labor groups but is opposed by environmental groups.

Most Democrats are adamant on leaving Keystone out of the measure, saying it's unrelated. Rather, they are pressing House Republicans to accept a bill based on the Senate measure, which doesn't include the pipeline.

"The Senate bill is a good bill that will create 2 million jobs. Let's get on with it," Pelosi said.

But Sessions insisted it was hypocritical for Democrats to demand a transportation "jobs bill" without the Keystone provision because the oil pipeline would create many well-paying jobs.

"Why are certain jobs OK and certain jobs are not?" (Republicans) are not trying to pick and chose," he said.

If the conference committee does not agree on a long-term bill or to the Houses temporary extension, federal funding for transportation is to expire June 30.

Meanwhile, in developments related to the highway reauthorization bill:

The House defeated a motion to instruct its conferees on the bill to limit spending for fiscal 2013 to $37.5 billion, which is $15 billion less than is allotted in the two-year Senate bill.

The nations governors and mayors held a conference call asking Congress to pass the surface transportation bill so local and state governments can firm up long-term plans on projects with certainty for funding.

Leaders of American Trucking Associations asked members of the conference committee negotiating the highway bill to address several critical issues for the trucking industry, including one calling for electronic onboard recorders.

The Owner-Operator Independent Drivers Association and a coalition of small-business groups announced their opposition to the EOBR provision.

Connecticut Gov. Dannel Malloy called Congress "crazy," "irresponsible" and "insane" for failing to approve a long-term transportation bill that would allow the states to move forward on new road projects.

House Speaker Boehner made an off-the-cuff remark that he is considering a six-month extension to push the issue past the November elections, infuriating scores of Democrats.