Democratic candidate Joe Biden has just won the Pennsylvania vote, election officials have said.
Biden has taken the lead over Trump by 5,587 votes, with 95% of the state’s precincts reporting.
The state could hand him the 270 electoral college votes needed to win.
A win in just Pennsylvania, which has 20 electoral college votes, or two of the other four remaining states would be enough to confirm Mr Biden as president-elect, barring any legal challenge.
Biden already pulled ahead of Donald Trump in Georgia, a key state in the US presidential race, voting data shows.
According to the most recent data, Mr. Biden is leading in the state by more than 1,000, with 99% of votes counted.
With its 16 electoral college votes, winning the state would put Mr. Biden just one vote shy of the crucial 270 threshold needed to win the presidency.
If Mr. Trump does not win Georgia, the most electoral college votes he could get from the remaining states is 269, which would leave the candidates in an unprecedented draw.
Final vote counting is continuing and no news has yet projected it as a Biden win.
Authorities said they hope to have final result on Friday.
Georgia is a traditionally Republican state and has not been won by a Democrat since 1992.
It is one of a handful of states on which the election now hangs.
The current state
Currently Joe Biden has 253 electoral college votes, while Republican’s Trump has 214. To win the White House, a candidate needs 270.
Biden has since received a higher tally projected a win for the Democrat in Arizona.
In addition to Georgia and Arizona, counts are continuing with razor-thin margins Nevada and North Carolina.
Trump needed to win Pennsylvania and three of the remaining four states.
Pennsylvania Secretary of State Kathy Boockvar told a press conference that most ballots would be counted by Friday, but the race was still too tight to declare a result.
When the going gets tough
Mr Trump is now leading in the state by fewer than 20,000 votes he has cut the Democratic candidate’s lead in Arizona to about 47,000 votes. CBS News has categorised the state, which carries 11 electoral college votes, as a ‘likely’ win for Mr. Biden.
[Mr. Donald Trump. Photo/courtesy].
Trump had a lead of more than 76,000 in North Carolina (15 electoral votes) with 96% of votes tallied
In Nevada, Biden has an edge of more than 11,000 over Mr Trump. The state has six votes under the electoral college system. An election official said the results from more than 51,000 postal ballots would be updated on Friday
A senior Trump administration official told CBS Trump did not plan to concede if Biden ultimately declared victory.
Trump has made unsubstantiated claims of election fraud.
Speaking from the White House on Thursday, the president said, “If you count the legal votes, I easily win. If you count the illegal votes they can try to steal the election from us.”