Iranian Foreign Minister Mohammad Javad Zarif and US Secretary of State John Kerry are working on new possible proposals aimed at facilitating a final deal on Tehran's civilian nuclear work, Press TV reported.
Zarif and Kerry, who had been set to leave the talks in the Austrian capital Vienna, decided to extend their stays for a meeting to discuss the new ideas on Friday night.
"Kerry has delayed his departure (for Paris)... in order to continue consultations" with Zarif, US State Department spokeswoman Jen Psaki said before the meeting.
Earlier in the day, the top Iranian diplomat also sat down for nuclear talks with Kerry and EU coordinator Catherine Ashton in Vienna.
Meanwhile, White House spokesman Eric Schultz said serious gaps still exist in the talks.
"Obviously, the deadline is Monday (November 24), and our folks there are working furiously to meet it... Serious gaps do remain," Schultz noted.
Reports say German Foreign Minister Frank-Walter Steinmeier and a Chinese delegation will join the talks on Saturday, while Russian Foreign Minister Sergei Lavrov is slated to arrive in Vienna on Sunday.
On Friday, Zarif said despite extensive negotiations between Iran and the P5+1 countries - Russia, China, France, Britain the US and Germany - they did not offer any significant proposals to Iran.
Sources close to the Iranian negotiating team say the main stumbling block in the way of resolving the dispute over Iran's nuclear energy program remains to be the removal of all the bans imposed on the country, and not the number of Iran's centrifuges or the level of uranium enrichment.
Tehran wants the sanctions entirely lifted while Washington, under pressure from the pro-Israeli lobby, insists that at least the UN-imposed sanctions should remain in place.