text: (CNN)Sen. Marco Rubio said he'll make a decision on running for president in the next few weeks and feels confident that he could obtain the resources to "credibly run a campaign and win," despite an increasingly crowded GOP field taking shape. 
  
  In a wide-ranging interview with CNN's Wolf Blitzer, the Florida Republican also gave his thoughts on Republican efforts to defund the president's executive action on immigration, and further explained why he won't support the administration's new Cuba policy. 
  
  2016 
  
  Rubio, who released a new book "American Dreams" on Tuesday, said he's still deciding whether he thinks he can be more effective as president or as a senator under the new majority. He has already said he won't run for both offices in 2016. 
  
  Marco Rubio: Radicalized individuals 'very real threat' to the West 
  
  With power players Mitt Romney and Jeb Bush now considered likely contenders, Rubio said "they're both credible and well-funded" candidates but argued there would still be room for his campaign if he decides to plow forward. 
  
  "I'm confident that if we decide to run for president ... we will have the funding and the resources necessary to credibly run a campaign and win," he said. 
  
  "But I understand that the longer you wait, the harder it becomes to do that," he added. 
  
  Romney tells donors he's considering 2016 bid 
  
  Bush and Romney have already been in active in talking with big-money supporters and securing financial resources, making it strategically more difficult for other potential contenders like Rubio to lock down support from the GOP's donor class. 