Joe Biden will be sworn in as US president on January 20 and he already has a lot to get on with.

The first 100 days of a new presidency has become something of a benchmark for how a president will get things done in their administration, after Franklin Roosevelt set a first 100-day standard when he took office in 1933.

Like many before him, the president-elect has promised a plethora of changes.

Climate change

Biden has been very clear that one of his first acts as president will be to rejoin The Paris Agreement.

The US formally left the pact in early November, after the Trump administration earlier told the United Nations in 2017 it intended to pull out of the agreement.

Biden says after rejoining the global commitment, he intends to rally the rest of the world to increase their climate targets and take further action to stop climate change.

Biden told a rally in Tampa just prior to election day that Florida saw the impacts of climate change more than most states.

"The economic toll is astounding and it grows every year, but the human toll is worse. Lost lives, lost homes, small businesses shattered," he said.

"We can change the path we're on. We've got to act now, time is running out."

He won't achieve it in his first 100 days, but hitting a net-zero emissions target by 2050 has been another key cornerstone of the Biden campaign — and he says he'll start that on day one of the job, by signing new executive orders to kickstart the plan.

He's also committed to convening a climate world summit and prioritising international agreements to reduce emissions in global shipping and aviation in those crucial first three to four months of his presidency.

COVID-19 pandemic recovery

With the US still recording more than 100,000 new coronavirus cases a day, Biden has promised he will establish a scientific advisory body straight away to try to get the pandemic under control.

When he declared his election victory, he told the world he would this week name leading scientists and experts as advisers to put his campaign's plan to control the virus into motion.

The president-elect has already named former surgeon general Vivek Murthy and former Food and Drug Administration commissioner David Kessler as co-chairs of the working group.

"Our work begins with getting COVID under control," Biden said in his victory speech.

"We cannot repair the economy, restore vitality or relish life's most precious moments, hugging our grandchildren and our children, birthdays, weddings, graduations, all the moments that matter most to us until we get it under control."

He promised the plan would be built on science, empathy and compassion.

As well as a series of financial commitments directly related to the pandemic, Biden says he'll immediately seek to restore the US's relationship with the World Health Organization, another global group the US withdrew from under Donald Trump.

Economy and employment

Before even claiming victory, Biden made a statement that economic recovery was one of the first things on his list.

"More than 20 million people are on unemployment. Millions are worried about making rent, putting food on the table," he said.

"Our economic plan will put a focus on a plan to a strong recovery."

He says he'll deliver immediate financial relief to working families and small businesses, as well as creating more jobs directly tasked to getting the pandemic under control.

Biden has been calling on the Trump administration to enact a four-point plan to better protect essential workers from coronavirus for some time now — there's a chance changes may be made before Biden's inauguration, but big changes to infection control in workplaces are expected early in his leadership.

He has also committed to immediately boosting personal protective equipment (PPE), paid sick leave and testing capabilities for workers.

As well as dealing with the economic and workplace health and safety impacts of coronavirus, Biden has pitched big plans for employment in the clean energy and sustainability sectors too.

He says he'll immediately invest in sustainable job creation, promising more than 250,000 jobs to counteract the impacts of dwindling mining jobs.

The president-elect is big on unions as well — he says he'll deliver a plan to "dramatically increase union density and address economic inequality" in his first 100 days.

Government and international relations

Biden has committed to immediately resuming daily press briefings at the White House, Department of State and Department of Defense, as well as taking "immediate steps" to renew alliances through his foreign policy vision.

This includes a specific focus on motivating other countries to address climate change — he's singled out pressuring China to stop coal export subsidies and pollution outsourcing as one of his first jobs.

Biden will also be faced with the task of patching up relationships with entire continents alienated by insensitive Trump generalisations.

South African columnist Barney Mthombothi says Africa's population of 1.3 billion is seeking respect and "a return to an American president who doesn't insult African countries," referring to Trump's remarks in 2018 that likened African countries to filthy toilets.

Biden has also pledged to strengthen Europe-US alliances and to support NATO, another group Trump showed disdain for.

German Chancellor Angela Merkel isn't exactly best mates with Donald Trump, and German Bundestag politician Peter Beyer says there's an opportunity for the relationship between the two countries to strengthen.

"The big difference will be in the communication, that we treat each other again with full respect as partners, allies," he told AP.

"President Donald Trump didn't always differentiate between friends and foes."

Immigration

Back in June, Biden committed to making changes to immigration and reversing Donald Trump's border family separation policies on his first day as leader.

"On day one, I'm going to send a legislative immigration reform bill to Congress to provide a roadmap to citizenship for 11 million undocumented immigrants who contribute so much to this country," he told NBC News.

"My immigration policy is built around keeping families together, modernising the immigration system by keeping family unification and diversity as pillars of our immigration system which it used to be (and) ending Trump's cruel, inhumane policy at the border to rip children from their mothers' arms."

In the same interview, he also told the US network he'd straightaway rescind the "un-American Muslim ban" and take immediate action to protect '"Dreamers" (undocumented immigrants brought to the US as children) from deportation, as well as restore refugee admission in his first 100 days.

"That's who we are, that's how my great-great-great-great-grandfather got here," he said.

"He got in a coffin ship in the Irish sea never knowing if he was going to make it, and made it to the United States of America in 1848."

The president-elect has also committed to a 100-day moratorium on deportations for migrants already living and working in the US, as well as stopping the plan to "build a wall" and use the money to improve border screening infrastructure instead.

Race, gender and other social issues

If the Violence Against Women Reauthorization Act of 2019 isn't already enacted before he takes office (which he's called for it to be), getting it moving will be on Biden's list for his first 100 days.

He's also committed to make enactment of the Equality Act during his first 100 days as President a top legislative priority, as well as immediately reversing Trump administration actions that allowed for discrimination against LGBTQ+ Americans.

In a town hall meeting just weeks before election day, Biden told the mother of a transgender child he'd "flat out just change the law" to protect LGBTQ+ Americans from discrimination.

"I promise you, there is no reason to suggest there should be any right denied to your daughter that your other daughter has a right to be and do," he said.

"None, zero."

He says federal resources will be put towards preventing violence against transgender women, particularly women of colour, in his first 100 days in office.

Biden says persistent systemic racism will be addressed on day one of his administration — a day that now has an official countdown ticking over.

He's already called on Congress to enact Kamala Harris's bill aimed at creating a dedicated task force to address racial disparities highlighted from the COVID-19 pandemic, something he's committed to eliminating when he's in office.