U.S. President Donald Trump's surprise opposition to emergency coronavirus aid and annual government funding passed by Congress has left Americans and global financial markets wondering whether Washington will iron out its differences or descend into chaos in the coming days.

Trump has not yet said whether he will veto the $892 billion for COVID-19 relief that is coupled with $1.4 trillion to fund an array of federal agencies through next September.

Here's how this standoff could play out:

Trump backs down

Trump signs the 5,500-page bill, despite Congress' refusal so far to meet his demands. He wants far larger coronavirus relief checks for Americans and major reductions to the foreign aid budget and another spending he has deemed wasteful.

Trump vetoes the bill

Trump rejects the bill that passed overwhelmingly in the House of Representatives and Senate. This would present Congress with two options:

1. Round up the two-thirds majority in both the House and Senate to override Trump's veto before the bill expires, and then it automatically becomes law.

2. Sustain the president's veto, a scenario likely if enough Republicans abandon the legislation, despite their earlier votes for passage. The bill is killed.

Trump does nothing

Trump runs out the clock within 10 calendar days (except Sundays) of receiving it from Congress, neither signing nor vetoing it. The situation is known as a "pocket veto."

This step is somewhat complicated because it normally only works when Congress is adjourned.

In this case, the calendar works in Trump's favour if he wants to kill the bill. Within that 10-day time frame, the current 116th Congress expires on Jan. 3 and the new, 117th Congress is sworn in. Bills die if they are not enacted during the Congress in which they are introduced.

That means it could be left to President-elect Joe Biden to deal with after he is sworn in on Jan. 20. Meanwhile, people who lost their jobs during the pandemic would suffer as unemployment insurance for more than 14 million expires on Dec. 26.

Without enactment of the bill, the U.S. government runs out of money at midnight Dec. 28. If this battle is not resolved by then, Congress must either pass its fourth stopgap funding bill since last September or federal agencies will not have money to fully operate beginning Dec. 29.

In that case, tens of thousands of government workers could be furloughed and programs interrupted.

If Congress does pass a temporary bill, Trump would have to approve it or the shutdown begins.