Trump's campaign manager Kellyanne Conway said that Mitt Romney's appointment could anger many of Trump's supporters. Pictured: Mitt RomneyReuters

Republican candidate Mitt Romney stepped up his attack on President Barack Obama on Wednesday by accusing the president of hiding his true positions.

The former Massachusetts governor, who is on the verge of clinching the Republican nomination, quoted Obama's recent remark to Russian President Dmitry Medvedev to prove his point that the "president is intent on hiding."

"He (Barack Obama) is intent on hiding. You and I will have to do the seeking," Romney said in a speech to a conference of news executives, referring to Obama's assurance to Russian president that he would be more flexibility to work on missile defense after the presidential elections.

Obama criticized Romney on Tuesday for supporting a Republican budget plan that would slash social programs.

Romney hit back at Obama, claiming that he had distorted lots of things.

"I looked at what the president said. There were just so many things that I found to be distortions and inaccuracies, it's hard to give a full list," Reuters quoted him as saying. "President Obama came here yesterday (Tuesday) and railed against arguments no one is making and criticized policies no one is proposing. It's one of his favorite strategies - setting up straw men to distract from his record," he added.