Putin on Thursday maintained that the law bans only "propaganda of nontraditional sexual relations among minors." He argued that it is "no infringement on the rights of sexual minorities" and insisted that European laws allowing gay marriage contribute to population declines.
The Russian law has prompted calls for boycotts of the 2014 Winter Olympics hosted by Russia in Sochi.
Putin said while some European nations have allowed gay marriages, "the Europeans are dying out ... and gay marriages don't produce children."
"Do you want to survive by accepting immigrants?" Putin said. "Society can't absorb such a number of immigrants. Let us make our own choice, as we see it for our country."
The new Russian law imposes fines of up to 5,000 rubles ($150) for individuals and 1 million rubles ($30,000) for organizations, plus stiffer penalties for propaganda on the Web or in the media. Foreigners who violate the law are also subject to fines, plus prison sentences of up to 15 days, deportation and denial of re-entry into Russia.
The law does not outlaw gay sex or explicitly ban participation in gay pride parades or promotion of LGBT equality online.
Putin made the comment at a conference of Russia experts in Valdai in northwestern Russia. He also made a joking reference to his friend, former Italian Prime Minister Silvio Berlusconi, who was convicted in June of paying for sex with a minor and pressuring public officials to cover it up.
"Berlusconi has faced a trial for living with women. They (prosecutors) wouldn't touch him if he were gay," Putin said.