TEHRAN, Iran – Iran agreed Monday to ship much of its low-enriched uranium abroad and then rolled out a new obstacle to nuclear compromise by insisting it would press ahead with higher enrichment — bringing it closer to being able to make atomic warheads.

The deal forged with Turkey and Brazil appeared to be another attempt to stave off U.N. sanctions — a doubtful endeavor judging by reactions from the United States and other Western powers.

The White House showed deep skepticism about the pact, warning it still allows Iran to keep enriching uranium toward the pursuit of a nuclear weapon.

“Given Iran’s repeated failure to live up to its own commitments, and the need to address fundamental issues related to Iran’s nuclear program, the United States and international community continue to have serious concerns,” White House press secretary Robert Gibbs said.

Still, by involving Turkey and Brazil, Iran ramped up the pressure on Washington over additional U.N. sanctions.

The deal moves these two influential Security Council members closer to Tehran and presents the U.S. and its Western allies with a bloc of developing nations that back Iran’s right to pursue a nuclear program.

In announcing the accord, Brazilian Foreign Minister Celso Amorim and his Turkish counterpart, Ahmet Davutoglu, said Tehran has the right to “a full nuclear fuel cycle, including enrichment activities for peaceful purposes” and condemned any new sanctions against Iran.

Both countries are important for Washington. Brazil is South America’s largest nation and has a dominant role on the continent, while Turkey, a key NATO ally and a traditional regional U.S. mainstay, has moved to develop an increasingly independent voice.

While they have no Security Council veto, both are skeptical of the U.S.-led drive for a fourth set of Security Council sanctions to punish Tehran’s refusal to stop its enrichment activities.

And the Iranian maneuver could weaken growing resolve by Russia and China — which do have veto power — to support new sanctions.

Moscow and Beijing were responsible for watering down the language of previous anti-Iran sanctions but appeared to swing behind the U.S., Britain and France recently.

The deal announced Monday mirrors a swap proposed last October in which Iran would have shipped the same amount of low-enriched uranium to Russia in exchange for higher-enriched material for its research reactor. That deal fell apart over Tehran’s insistence that the swap take place on Iranian soil.

On its face, the latest plan seems a significant concession, with Iran agreeing to ship its material to be stored in Turkey and wait up to a year for higher-enriched uranium from France and Russia.

However, Iran is believed to have much more nuclear material stockpiled now.

In October, swapping 2,640 pounds would have left Iran with less than the 2,200 pounds of material needed to produce enough weapons-grade uranium for a bomb.

Since then, Iran has continued to churn out low-enriched material and started enriching uranium to an even higher level — from 3.5 percent to nearly 20 percent. While Tehran insists it has no nuclear arms ambitions, it could produce weapons-grade uranium much more quickly from the 20 percent level.

In March, the International Atomic Energy Agency said Iran’s stockpile stood at around 4,600 pounds. It has likely grown to an estimated 5,000 pounds, or more than twice the amount needed to produce enough material for a bomb, according to David Albright of the Washington-based Institute for Science and International Security, which has tracked Iran for signs of covert proliferation.

From the West’s point of view, that destroys much of the incentive for an agreement — and Iran’s decision to continue its program to enrich to near 20 percent poses an even greater hurdle.

Western nations insisted Monday they remained on the sanctions track.

For his part, Russian President Dmitry Medvedev cautiously welcomed the agreement but said it may fail to fully satisfy the international community.