"I'm not prepared to express wild optimism, but I think we are further along today than we were yesterday," Obama told reporters late last night after meeting with House of Representatives Speaker John Boehner, the top Republican in Congress, and Senate Majority Leader Harry Reid, the top Democrat in Congress.

"There's no deal yet unfortunately," Steny Hoyer, the No. 2 Democrat in the House, told NBC's "Today" programme earlier. "I think we're very close. I think we've come 70 percent of the way in terms of dollars. That's a long way to go in trying to reach compromise."

Democratic aides said the two sides remain at odds over the Republicans' proposed birth control restrictions in the package, while Republicans said they differed over how much to cut from current spending levels.

The showdown is over funding the federal government for the remainder of the current fiscal year, which ends September 30.

Without an agreement on spending for the next six months, money to operate the government runs out at midnight tonight (0400 GMT tomorrow) and agencies such as the Internal Revenue Service would have to begin a partial shutdown.

A government shutdown would idle hundreds of thousands of government workers, potentially put a crimp on the US economic recovery, and carry political risks for both Democrats and Republicans who could be seen by voters as failing to make compromises.

A shutdown would continue until Republicans and Democrats either resolve their differences or pass a temporary funding bill. Vital services such as national defense, law enforcement, emergency medical care and air traffic control would continue.

"What we're going to be trying to do is to make sure that we keep the government operating over the next seven days with a very simple agreement. We call it a clean CR (continuing resolution) -- a jargon which simply means that we're going to keep things going as they're going now while we are negotiating and trying to reach a deal," Hoyer said.

Obama, who has held four face-to-face meetings with the Republican and Democratic congressional leaders over three days, said a few "difficult issues" still must be resolved. He did not provide details.

Repeatedly over the past few days, optimism over prospects for a deal have been dashed, prompting the two sides to accuse each other of acting to shut down the government for the first time since the mid-1990s.

But Boehner and Reid managed to issue a joint statement after their latest meeting with Obama.

"We have narrowed the issues, however, we have not yet reached an agreement. We will continue to work through the night to attempt to resolve our remaining differences," they said.