US President Barack Obama speaks before signing a presidential memorandum on reducing the burden of student loan debt in the East Room of the White House in Washington. Picture: Larry Downing

Washington -

US President Barack Obama on Monday struck out at the literal and political constraints hemming him in during an increasingly contentious second White House term.

Obama went off script to eviscerate Republicans blocking plans to ease the huge burdens in student debt many Americans carry when they graduate from college.

Then Obama marched out of the White House to visit a Starbucks down the street, in a rare unannounced foray outside the security bubble in which US presidents live.

“The bear is loose,” Obama declared as he walked out the White House gate, testing his Secret Service detail.

Obama has been showing increasing signs of frustration with his political plight, after failing to move significant reform legislation on Capitol Hill since his second inauguration in January 2013.

A string of rows including over a scandal in delays to veterans health care and a firestorm over a Taliban prisoner swap to free US soldier Bowe Bergdahl are also bearing down on the besieged White House.

On Monday, Obama poured special disdain on Republicans who oppose a Democratic plan to close tax loopholes for millionaires to provide funds for graduates to refinance outstanding student loan debt at lower rates.

“You would think that if somebody like me has done really well, in part because the country's invested in them, that they wouldn't mind at least paying the same rate as a teacher or a nurse,” said Obama.

“I want Americans to pay attention to see where their lawmakers' priorities lie here. Lower tax bills for millionaires or lower student loan bills for the middle class. This should be a no-brainer.”

The bill has little chance of making it through Congress where Republicans control the House of Representatives and can block legislation in the Democratic Senate.

So, Obama, as he has done repeatedly this year, invoked his executive power to take his own measures - albeit ones that pale in comparison to what Congress could do.

Among his actions, Obama directed that annual student loan repayments be capped at 10 percent of a graduate's income - to help defray a situation where young Americans with new degrees struggle financially.

The White House says 71 percent of those who receive a bachelor's degree graduate with debt averaging nearly $30 000, and many take years to pay it off.

After his fiery student loan event, Obama threw off his jacket and strolled with his Chief of Staff Denis McDonough through the sticky early summer heat to a Starbucks along Pennsylvania Avenue near the White House.

His abrupt departure surprised White House staff, as well as reporters and photographers who follow the president everywhere - sending the press pack running to the wrong coffee shop.

A beaming Obama returned to the White House relishing his bolt for freedom, in which he shook hands with tourists and chatted with a hot dog vendor, after telling journalists who caught up with him to give him space.

It was not the first time in recent weeks that Obama sought to slip the constraints of office.

Several weeks ago he strolled past delighted tourists to an event at the Interior Department.

Last week, he made a rare diversion from the packed programme of one of his foreign trips to dine with friends at a plush Paris restaurant. - Sapa-AFP