WASHINGTON (AP) — Bills necessary to avoid shutdowns of federal transportation and aviation programs are high on Congress' to-do list when it returns to work next week.

President Barack Obama says as many as 1 million jobs are at risk without action.

Both the White House and House Republicans signaled Wednesday that they want to avoid such a scenario, but that doesn't mean it will be easy.

Federal highway programs, and the fuel taxes that pay for them, will expire Sept. 30 unless Congress passes short-term extension legislation. It would be the eighth such stopgap effort in the past two years. Funds for hundreds of construction projects across the country would be held up without passage.

Similarly, authority for the Federal Aviation Administration expires Sept. 16. The agency has been operating under a series of 21 short-term extensions since 2007. A standoff between the House and Senate partially shut down the FAA for two weeks this summer. Nearly 4,000 employees were furloughed, more than 200 stop-work orders were issued for airport construction and other projects, and tens of thousands of workers in construction-related industries were laid off.

Layoffs in the ailing construction industry would be many times greater than that if highway programs expire, transportation experts said.

"It's inexcusable to put more jobs at risk in an industry that's already been one of the hardest hit over the last decade," Obama said during a speech in the Rose Garden. He called on Congress to pass both the highway and FAA bills.

The president said 4,000 workers would be immediately furloughed without pay if the highway program isn't extended, and a significant delay could lead to 1 million workers losing their jobs over the next year.

Republicans were swift to respond that they want to pass both bills as well, even while accusing Obama of scare tactics and blaming Democrats for creating the legislative mess.

"During their control, they neglected aviation legislation for more than four years and left major transportation legislation in the ditch for more than a year," Rep. John Mica, R-Fla., chairman of the House Transportation and Infrastructure Committee, said in a statement.

Mica said he's willing to support a short-term extension of transportation programs, but just this once. He also left the door to a short-term FAA extension, but said he wanted to consult with House GOP leaders first.

Transportation programs — road and bridge repairs and transit subsidies — have wide, bipartisan support in Congress. The problem is money. Revenue from the 18.4 cents a gallon federal gas tax and 24.4 cents a gallon diesel tax that pay for programs is declining.

With House Republicans determined to force the government to live within its means, and Senate Democrats reluctant to cut core programs, almost any bill with a price tag requires a struggle for passage — even disaster relief for hurricane victims.

"Everything is in gridlock, and transportation happens to be visible and suffering largely because of an accident of timing," said transportation consultant Mort Downey, a former Obama adviser. "The same problem would be occurring with other programs if they were up for extension."

Mica is pushing for a six-year extension that would cut spending by 30 percent in order to live within expected revenues. A Senate proposal would extend the program only two years, maintaining current spending, and cost $109 billion.

Since passage of either bill by the Sept. 30 deadline isn't realistic — the bills haven't been formally introduced yet, only outlined by their sponsors — a short-term extension is necessary. But it's possible the House and Senate will clash over whether to keep spending at current levels in a short-term bill, which would mean dipping into the general treasury, or to reduce spending.

"We're still running all of our numbers with respect to short-term and long-term, and ultimately our goal is to ensure that the trust fund remains solvent ... that we don't continue to rely on general fund bailouts," Caroline Califf, a spokeswoman for Mica, said in an email.

Also unclear is whether Mica will try to attach extraneous provisions to either must-pass bill in an effort to push through policies not already agreed to by the Senate. That's what happened on the FAA bill this summer, precipitating the shutdown.

It's unlikely Republicans will try a similar gambit on the transportation bill, Downey said in an interview.

"I think this is too big, too widespread, has too many consequences, too much of a real opportunity for the president to bash them," he said.

Labor issues have been the key holdup for a long-term FAA bill. Three years ago it was a contract dispute involving air traffic controllers. That issue was resolved, but then a fight between FedEx and United Parcel Service over whether FedEx workers should have to operate under the same restrictive labor rules as UPS held up passage in the last Congress. This time, the issue is a provision in the House FAA bill that would reverse a National Mediation Board ruling last year, making it more difficult for airline workers to unionize.

There are other potential holdups as well, including a dispute over landing slots at Reagan Washington National Airport and safety rules for the air transport of lithium batteries.