Republican presidential candidate Ron Paul will not campaign in states with upcoming primaries, his campaign said Monday.

We will no longer spend resources campaigning in primaries in states that have not yet voted, the statement said. Doing so with any hope of success would take many tens of millions of dollars we simply do not have.

Paul will continue his efforts to accumulate delegates to the Republican National Convention in August, the statement said, although presumptive nominee Mitt Romney's lead in delegates appears to be insurmountable at this point.

Despite failing to win a single state primary, the longtime Texas libertarian congressman has steadily picked up delegates while espousing a steady message of limited government -- something that has resonated loudly in the era of the Tea Party -- calling to eliminate to the Federal Reserve and vowing to bring home American troops deployed across the globe. In his latest under-the-radar success, Paul recently captured most of the available delegates in Nevada and Maine.

But the relentless demands of the primary, particularly the type of fundraising necessary to compete with Romney, appear to have taken their toll. In the statement, Paul urged his backers to sustain a grassroots movement.

I hope all supporters of liberty will remain deeply involved -- become delegates, win office and take leadership positions, Paul said in the statement. In the coming days, my campaign leadership will lay out to you our delegate strategy and what you can do to help, so please stay tuned.