Congressional Republicans are facing several key hurdles to considering and passing an immigration bill when they return next week, which some say is already making it unlikely that they’ll be able to meet President Trump’s new demands for tough new legislation.

The president has tweeted since Sunday that the constant threat of illegal immigration across the U.S.-Mexico border demands a border wall and more border security, and he proposed new ideas for legislation aimed at tightening up federal immigration laws to allow for longer detentions of illegal immigrants, among other changes. Even before the weekend, Trump was known to be disappointed after getting just a fraction of the $25 billion in border funding he wanted in the omnibus spending bill that he ultimately signed.