Republican Sen. Ted Cruz (Tex.) waves after speaking at the Freedom Summit in Des Moines, Iowa, last month. (Charlie Neibergall/AP)

Sen. Ted Cruz (R-Tex.)  reiterated Sunday that he is looking at the possibility of a presidential campaign "very, very seriously" but declined to hit back against criticism lobbed at him by a fellow Texas Republican.

In an interview with The Washington Post this week, former Texas governor Rick Perry jabbed at Cruz, noting that President Obama was also a young U.S. senator when he was elected as president.

“I think it’s one of the selling points, if you will, to the American people as they decide who is going to follow Barack Obama,” Perry said. “I think they’re going to make a rather radical shift away from a young, untested United States senator whose policies have really failed.”

Cruz, speaking on CNN's "State of the Union," shrugged off the criticism and said that Perry had done a good and effective job as governor.

"People occasionally throw rocks in politics," Cruz said. "That's his choice."

Cruz said on ABC's "This Week" that former Florida governor Jeb Bush (R) is going to have to "make the case" to Republican primary voters about his record, including his support for the Common Core standards and stance on immigration.

"What I would urge every Republican thinking about running to do -- and this is true of senators, of governors -- stand up and lead," Cruz said. "I'd be thrilled if six months from now, we have a half dozen Republicans standing and leading and making the case. There is a better way."

Cruz appeared on both programs from Germany, where he is attending the Munich Security Conference.

He said he believes the United States should provide arms to Ukraine to counter Russia.

"When it comes to Russia and Ukraine, the path we’re on doesn’t make any sense," Cruz said. "We need to be providing defensive arms to the people of Ukraine."

The senator said that the United States should also directly arm peshmerga ground forces fighting against the Islamic State.

" I don't believe, right now, we need American boots on the ground, and the reason is we have boots on the ground already with the Kurds. The peshmerga are trained, effective fighters. They are close allies of us," he said on ABC.

Cruz lashed out against both the Republican leadership and Congressional Democrats regarding a standoff over a spending bill to fund the Department of Homeland Security. The bill would strip away changes made by Obama's executive actions on immigration.

Cruz said it is up to Republican leaders to lay out their strategy, which he said he has told them would not succeed. He also took aim at what he called the "stunning irresponsibility" of Senate Democrats for "holding national security hostage for partisan political objectives."