President Barack Obama and the United States favor illegal migration in Europe because they want to fill it up with Muslims, the chief of staff of Hungarian Prime Minister Viktor Orban said Thursday.

Janos Lazar also described Hungarian-born American financier George Soros as a standard-bearer for Obama's immigration policies for Europe and said "certain American groups" want Europe to be "diluted ... so Europe and America can cooperate without restraint."

White House spokesman Josh Earnest said he was unaware of Lazar's comments, but added: "I'm not sure they're worthy of a response."

Lazar called Soros a patron of former U.S. President Bill Clinton and Hillary Clinton, the current U.S. presidential candidate, and a Democratic Party supporter who was "ready to step up" against Orban.

"Not so long ago while visiting Europe, President Obama clearly spoke out in favor of the importance of migration, settlement and even the forced settlement (of migrants)," Lazar said at a news conference. Obama and America "are following a very strong pro-migration, pro-illegal migration policy in the interests of having as many Muslims as possible in Europe."

Orban has said that he wants no immigration from outside Europe and that Hungary will solve its demographic problems and dwindling workforce with policies like higher subsidies for families with children.

Hungary late last year built fences on its borders with Serbia and Croatia after nearly 400,000 migrants passed through the country on their way to Germany and other western European destinations.

"Our conviction is that the borders of Europe have to be defended," Lazar said. "If the countries of Europe need immigration, it can be possible only in a limited, controlled manner."

The government is also sponsoring a referendum expected to be held by October against a plan by the European Union to resettle refugees in Italy and Greece to other countries in the bloc.

Obama and the Clintons have criticized Orban for his perceived authoritarianism and efforts to crack down on civic groups like those advocating for Roma or gay rights. Orban considers some of these groups "paid foreign activists."

Since returning to power in 2010, Orban has also faced frequent criticism from the U.S. and the European Union for eroding democratic checks and balances, striving to build an "illiberal democracy" and using state funds to build up pro-government media. Hungary's migrant policies, including anti-migrant billboards, curtailed social benefits for asylum-seekers and repeated remarks equating migration with terrorism, have been denounced by the United Nations' refugee agency.