(Adds defence minister in paragraphs 6, 7)

FRANKFURT, Nov 11 (Reuters) - German chancellor Olaf Scholz's governing coalition has agreed in principle to double the country's military aid for Ukraine next year to 8 billion euros ($8.5 billion), a political source in Berlin said on Sunday.

If approved by parliament, where Scholz's parties hold a majority, the boost would lift Germany's defence spending to 2.1% of its gross domestic product target, beyond the 2% pledged by all North Atlantic Treaty Organization members, the source added.

Lawmakers from Scholz's Social Democrats, the Free Democrats and the Green party agreed on the increase in negotiations over the proposed 2024 federal budget ahead of a formal meeting of the budget committee of the Bundestag - or lower house of parliament - on Thursday, Nov. 16, the source said.

Bloomberg News first reported on the news on Saturday, citing people familiar with the matter.

A spokesperson for Germany's Ministry of Defence said the Bundestag committee has not finished negotiations and declined to comment further.

Defence minister Boris Pistorius, interviewed by broadcaster ARD, referred to the planned doubling of military aid to Ukraine.

"It is a strong signal to Ukraine that we will not leave them in the lurch," he said, adding the move, if agreed, would mean the annual budget allocation would be enough to last the whole year.

Germany's Bild am Sonntag newspaper had also said the committee is due to approve the additional 4 billion euros.

"Doubling the military spending is both the right thing to do and important," it quoted member of parliament Andreas Schwarz, who acts as an SPD military budget official, as saying.

"With the move we will underscore our promise to Ukraine with the necessary funds. The fact that we will also be able to fulfil our NATO obligation is a great success of the ... coalition," he was reported as saying.

A European Union plan to spend up to 20 billion euros ($21 billion) on military aid for Ukraine is meeting with resistance from EU countries, diplomats said this week.

($1 = 0.9362 euros) (Reporting by Gursimran Kaur in Bengaluru, Holger Hansen in Berlin, writing by Vera Eckert in Frankfurt; Editing by David Gregorio, Kirsten Donovan and Giles Elgood)