By Krisztina Than BUDAPEST (Reuters) -Tens of thousands rallied in Budapest against Prime Minister Viktor Orban on Saturday, waving the national flag as the leader of the surging opposition Tisza party pledged to make Hungary part of a strong Europe and end Orban's 15-year rule.

Orbán, a Trump ally, has applauded the U.S. administration’s actions to dismantle the U.S. Agency for International Development, claiming, with no evidence, that it was used to fund liberal causes in Hungary aimed at toppling his government.

Orbán, in power since 2010, has used the March 15 celebration in recent years as a podium from which to launch increasingly hostile harangues against the EU, to which Hungary has