The issue of gun control has been one of the most intractable for President Barack Obama during his two terms in office.

Despite a large number of mass shootings, and public support for some legislation, lack of congressional support and a strong pro-gun lobby has stymied attempts at change.

Coming to his last year in the White House, Mr Obama is proposing a raft of executive actions to tackle gun violence in the United States.

Here's a look at one of the most divisive issues in America:

How serious is the problem?

The estimated number of guns held by civilians in the United States, both legal and illegal, is between 270 million to 310 million.

There are between 88.8 to 101 guns per 100 people in the US, the highest proportion in the world. The second-ranked country, Yemen, has an average of 54.8 guns per 100 persons, according to data in the Small Arms Survey 2007.

There were 353 mass shootings in the US as of Dec 3, 2015 and gun violence claims more than 30,000 lives in America each year, over half of them suicides.

What is the state of gun control today?

It is illegal in the US for certain people to own firearms. These include people convicted of certain crimes, drug addicts, those who have been committed to a mental institution and veterans who left the military with a dishonourable discharge, among others. The full list is here.

Licensed gun dealers conduct a background check on customers to see if they are among those prohibited from owning a gun.

But there are a number of loopholes, said the New York Times. The main one being that many private sellers, including those who sell at gun shows, are not required to do background checks on buyers.

State laws differ widely, with places like Wyoming, Mississippi and Kansas being the most lax while New York, California and Connecticut among the strictest.

Some states have more stringent background check systems and some require a licence or permit to own a gun. Laws on carrying weapons vary from state to state.

From 1994 to 2004, it was illegal to sell many types of assault rifles and high-capacity magazines, but the law has lapsed.

What are the arguments against gun control?

The right for Americans to own guns is enshrined in the Constitution and deeply embedded in the nation's psyche.

Legal debates often come down to the Second Amendment, which states: "A well regulated militia being necessary to the security of a free state, the right of the people to keep and bear arms shall not be infringed."

Gun rights advocates say that refers to an individual's right to gun possession, while gun control advocates say it means the people's collective right, through a militia.

A 2008 Supreme Court judgment ruled in favour of the first interpretation - that "the people" referred to individuals. Those in favour of the right to own guns stress citizens' right to self-defence.

The National Rifle Association's executive vice-president Wayne LaPierre famously declared that "the only thing that stops a bad guy with a gun is a good guy with a gun".

What are the arguments for gun control?

People who advocate gun control argue that the more firearms there are, the more likely they will be used. Thus, disputes escalate to violent clashes, and crimes and attacks are more likely to be fatal.

They say that responsible gun laws would help prevent crime and deaths while still allowing for law-abiding citizens to own them.

Most of the weapons used in recent mass shootings were obtained through legal means, and those who support gun control strongly advocate curbs on guns with high-capacity magazines such as assault rifles.

They also argue that the chance that an armed civilian can prevent a shooting is negligible.

Where does the American public stand?

A 2014 survey by the Pew Research Center showed that for the first time since 1993, a higher percentage of Americans (52 per cent) said it was more important to protect the right of citizens to own guns than to control gun ownership.

However, a survey in 2013 by the centre showed that specific gun control measures had strong support from the public.

These include background checks for private sales and sales at gun shows (85 per cent), and preventing people with mental illness from buying guns (80 per cent).

Why are gun laws so hard to pass?

Congress has not approved major gun-control legislation since the 1990s.

Over the past generation, American politics have become more bitterly partisan, and regional divisions more rigid.

As a result, gun control has become an increasingly partisan issue, with Republicans more uniformly opposed - at a time when Congress and most state houses are in Republican hands.

Republican politicians often face constituents who are against gun regulation and victorious candidates can be supported by deep-pocketed pro-gun lobby groups like the National Rifle Association .

What is Mr Obama's plan to address this issue?

A major loophole that Mr Obama's executive action aims to plug is the so-called 'gun show loophole'.

Currently, licensed firearms dealers are required to perform background checks on customers by submitting their details to the FBI, which checks it against databases (the process takes a few minutes).

But there are provisions under US gun laws for individuals to sell firearms privately and at gun shows without making background checks on the buyer.

A major part of Mr Obama's action will broaden the definition of a gun dealer so that more buyers will undergo background checks.

The plan targets small-scale gun sellers, who may conduct transactions from home, a gun show or via the Internet.

Other measures include hiring more people to run the FBI background check system, a rule requiring background checks for buyers of dangerous weapons from a trust, corporation or other legal entity and and requesting from Congress an additional US$500 million to increase access to mental health care.

Will Mr Obama's latest action work?

Legal experts said such executive action alone can increase the number of gun buyers who have to get a licence, but will not close the loophole.

However, the move could have an indirect effect on preventing gun deaths by disrupting the supply chain to the underground market.

The proposed measures are also unlikely to address the hundreds of millions of guns already thought to be in circulation in the United States.

Already some Republican candidates seeking the party's nomination for the 2016 election have said they would overturn any gun control measures by Mr Obama if they get into office.

Sources: BBC, Bloomberg, CNN, New York Times, Reuters, Small Arms Survey, Washington Post