It's back to school for children and back to work for Congress and President Barack Obama - and what a September it is likely to be.

The Obama administration faces a number of challenges in the weeks to come, including getting Congress to pass a funding Bill by the end of next month to prevent another government shutdown, convincing lawmakers not to reject the Iran nuclear deal, and preparing to host Chinese President Xi Jinping, at a time of hacking allegations and rising Chinese assertiveness in the South China Sea.

Some observers say the agenda Congress faces looks to be a challenging one, especially with the 2016 presidential election looming and presidential candidates unwilling to fall in line as they hope to make their views heard.

But the Iran nuclear deal will dominate the agenda in September, as Republican lawmakers attempt to gather enough support to override a presidential veto of the resolution of disapproval.

In the Senate, a two-thirds majority vote - or 67 votes - is needed to override Mr Obama. That means at least 13 Democrat votes are necessary to kill the deal, which seeks to prevent Iran from obtaining a nuclear weapon.

This is an even more daunting task in the House of Representatives, where at least 44 Democrat votes are needed.

House Minority Leader Nancy Pelosi said last Thursday she is confident that the President's landmark deal would not be halted by Congress. The deadline for the first vote is Sept 14 - barely a week after the autumn session starts on Sept 8.

But even if Republican lawmakers are unable to stop the deal at this juncture, Professor Daniel Franklin, associate professor of political science at Georgia State University said: "There is still the issue of whether the procedure that was followed in the adoption of this agreement was constitutional."

He said senators could argue "that the agreement is actually a treaty that is required to go through the ratification process". This means it requires the approval of two-thirds of the Senate.

"At that point the issue will go to the courts and, in my opinion, the Iran Agreement will not withstand a legal challenge," Prof Franklin said.

But that is not all Congress has to contend with this autumn. Funding legislation will have to be passed by end-September to avoid a shutdown similar to the one in 2013.

With conservatives up in arms about the funding of Planned Parenthood, a group that provides reproductive healthcare services including abortions, passing any funding measures might prove tricky.

Experts say a shutdown is unlikely, as Republicans do not wish to shoulder the blame for that going into the 2016 election, but Congress is also unlikely to pass its budget on time.

"The result will be the passage of a series of continuing resolutions that more or less fund government at pre-existing levels" to keep the government running, said Prof Franklin.

While all this is at play on Capitol Hill, Mr Obama will also have a slew of other obligations, including the first state visit by China's President to the United States. The leaders will navigate issues such as climate change and territorial disputes in the South China Sea.

While the date of that visit has yet to be finalised, a visit by Pope Francis to the White House is set for Sept 23. The Pope will also address Congress the next day.

With deadlines to meet, state visits, and the fate of the Iran deal still hanging in the balance, experts are expecting an eventful autumn, to say the least.

As Prof Franklin said: "In the recent era of hyper partisanship, divided government is that much more difficult to navigate."