Media playback is unsupported on your device Media caption Rajini Vaidyanathan looks at what services might be cut if there is a partial government shutdown

US President Barack Obama has urged lawmakers to "act like adults" and come to a deal on a budget to avoid a looming government shutdown.

"Some folks are trying to play politics about what should be a simple discussion," he said in Pennsylvania.

Mr Obama spoke as budget talks intensified in Congress. Without a deal, the US government will shut down at midnight on Friday.

Republicans and Democrats are at odds over the size of spending cuts.

Mr Obama, Republican House Speaker John Boehner and Senate Democratic Majority Leader Harry Reid met in the Oval Office at the White House late on Wednesday.

Mr Obama said the meeting had been "constructive" and narrowed the gaps between them, but no deal had yet been reached.

Republicans, urged on by the anti-government Tea Party movement, are calling for a far greater reduction in the government budget than Democrats are willing to concede, in what Republicans describe as a necessary effort to trim the $1.4 trillion (£858bn) US budget deficit.

"Our goal is real clear," Mr Boehner said on Wednesday.

"We're going to fight for the largest spending cuts we can get... because we believe that cutting spending will lead to job creation."

Meanwhile, Democrats have accused Republicans of linking social policy agendas to the bill, and say the size of the cuts Republicans demand would hinder the nascent US economic recovery.

Analysis I am just back from the Capitol, where I spoke to people at a Tea Party rally. Their view on a potential shutdown this weekend might be summed up as "bring it on!" They were chanting: "Shut it down!" Several made the point that if non-essential parts of the government shut down, they'd be quite happy. If it's not essential, the view is, then the government shouldn't be doing it anyway. I suspect there will be a deal. There is too much for both sides to lose in the blame game that would follow. But the strength of the Tea Party has already made it hard for the Republican leadership to compromise, and will make selling any deal tough. Mr Obama and the Democrats don't have quite the same problem, but the cuts he has accepted have already upset supporters. Read Mark's thoughts in full

Republicans in the US House have pushed for $61bn (£37.4bn) in cuts over last year's spending between now and the end of the fiscal year on 30 September, and have sought to use the budget bill to dismantle Democratic policy priorities.

Democrats have resisted, arguing the cuts could imperil the fragile economic recovery.

The US government has subsisted without a long-term budget since 1 October, funded by a series of temporary measures.

The most recent of those is set to expire at midnight on Friday, forcing all government services deemed non-essential to shut down and keeping hundreds of thousands of government workers at home.

Republicans have proposed another temporary measure - but one that would cut $12bn from spending in a single week. Mr Obama has rejected that, saying the US government cannot continue to operate on a week-to-week basis.

'Not how it works'

The Democrats said the two sides had settled in recent days on $33bn in budget cuts, but Mr Boehner subsequently denied a deal was struck.

On Wednesday, Mr Obama said the Democrats had compromised and called on Republicans to do so as well, saying they could not simply have their way.

"That's not how it works," he said.

Mr Obama said a government shutdown would harm the US economy, keep businesses from getting loans and prevent families from being able to tour national parks.

Also Wednesday, Democratic Senator Dick Durbin said negotiators had made progress, but he said conservative Republicans' policy prescriptions - including cutting funding for women's health group Planned Parenthood and attacking the Democrats' 2010 healthcare overhaul and financial reforms - had stymied the talks.

Government shutdowns US government shut down 10 times during the Carter and Reagan administrations

Last shutdown was in 1995 under President Bill Clinton

Law passed in 1870 prohibits government from operating if a budget hasn't been passed

This is interpreted to exempt so-called essential services

These include: National security, air traffic control, some but not all medical services

But not: Processing of visas and passports, museums and monuments, answering work emails (by non-essential workers) What 'government shutdown' means

"There's been a direct negotiation - things put on the table that had not been discussed before and I think we're moving towards closure," said Mr Durbin of Illinois, the number-two ranking Democrat in the Senate.

Mr Obama and Mr Boehner spoke on the phone for three minutes on Wednesday morning, with Mr Boehner saying he was hopeful a deal could be struck, his office said.

Democrats also complained on Wednesday that Mr Boehner had shifted the amount of spending he was seeking to cut from $33bn to $40bn. But Mr Boehner's office denied there had ever been an agreement on the first figure.

"Every time we agree to meet in the middle, they move where the middle is," Mr Reid said.

"The speaker has a choice to make, and not much time to make it. He can either do what the Tea Party wants or what the country needs," he added.