TBILISI (Reuters) -Georgia's parliament was set on Tuesday to debate the second reading of a bill on "foreign agents" which has been described as authoritarian and Russian-inspired by Georgia's opposition and Western countries.

The bill, which has sparked protests, would require organisations receiving more than 20% of their funding from abroad to register as "foreign agents".

Parliament, which is controlled by the ruling Georgian Dream party and its allies, is likely to approve the bill, which must pass one more reading before becoming law.

Local media cited Georgian Dream faction leader Mamuka Mdinaradze saying that the debate would run until 1700 GMT and that voting could be postponed till later in the week.

Georgian critics have labelled the bill "the Russian law", comparing it to Moscow's "foreign agent" legislation, which has been used to crack down on dissent there.

Russia is disliked by many Georgians for its support of the breakaway regions of Abkhazia and South Ossetia. Georgia lost a brief war with Russia in 2008.

The United States, Britain and the European Union, which granted Georgia candidate status in December, have criticised the bill. EU officials have said it could halt Georgia's progress towards integration with the bloc.

On Monday, former prime minister Bidzina Ivanishvili, the billionaire who founded the ruling Georgian Dream bloc and remains influential inside it, harshly criticised the West in a speech to a pro-government rally in Tbilisi.

Ivanishvili told tens of thousands of attendees, many of whom had been bussed in from Georgian provinces by the ruling party, that a "global party of war" had hijacked the EU and NATO and that it was bent on using those institutions to undermine Georgian sovereignty.

Ivanishvili, who says he wants Georgia to join the EU, said the foreign agent law would bolster national sovereignty, and he suggested that the country's pro-Western opposition was controlled by foreign intelligence services via grants to NGOs.

"This money has nothing to do with help, in fact their only aim is the loss of Georgian sovereignty," he said.

He added that after elections due by October, Georgia's opposition, which is dominated by the United National Movement party of former President Mikheil Saakhashvili, would face "the harsh political and legal judgment it deserves".

(Reporting by Felix Light, Editing by Timothy Heritage and Gareth Jones)