Democrat Joe Biden took the lead in key battleground state Pennsylvania on Friday, where a victory for the former vice president would push him past the threshold of electoral votes needed to win the White House, official data showed.

More ballots are yet to be counted, but shortly before 1400 GMT, Biden had moved ahead of incumbent President Donald Trump by more than 5,500 votes, according to official provisional results from the state government.

Biden currently has at least 253 electoral votes. The magic number is 270. If he wins Pennsylvania -- a state won by Trump in 2016 -- and its 20 electoral votes, he would pass that threshold.

US networks have said so far the race is still too close to call. 

Biden is also currently in the lead in key states Arizona, Georgia and Nevada. Fox News and the Associated Press have already called Arizona in Biden's favor, but other US media have said the race is still too close to call.

Trump has amassed 214 electoral votes so far, with his path to victory narrowing. The Republican incumbent has made unsubstantiated claims of massive voter fraud.