Iran test-fired several of its longest-range missiles Monday, topping off a dramatic four days in which it also tested medium-range missiles and revealed it has been developing a secret nuclear facility. The developments are adding to the sense of urgency as world powers prepare to meet with the country about its nuclear program on Oct. 1.

The latest tests came as the United States announced another move likely to complicate already contentious talks: that it will pursue tougher economic sanctions against Iran.

The Obama administration is moving fast to assemble the new package of sanctions, which might include blacklisting a large number of Iranian banks and cutting off investment to Iran’s oil and gas industry.

The move has already sparked criticism from US allies and observers: China said it will not support the move, Iraq said the sanctions won’t work, and Israel is demanding even tougher sanctions.

The announcement of more severe sanctions is the latest in a week of tense developments around Iran’s nuclear program. Last week, U.S. officials announced that Iran has been developing a secret nuclear facility in the city of Qom, as the Christian Science Monitor reported, noting that the revelation is likely to “raise the stakes for a scheduled Oct. 1 meeting between Iranian and Western negotiators on the nuclear issue.”

Days later, Iran raised the stakes again by testing a missile-launching system near the site of the Qom facility.

The missiles fired Monday have the longest range in Iran’s arsenal. They can carry a warhead and reach Israel, US military bases in the region, and some areas in Europe, according to the Associated Press.

The incidents have sparked outrage from Israel, which has refused to rule out the possibility of a unilateral strike on Iranian nuclear facilities but has also encouraged the US to seek “crippling” sanctions first. British Foreign Secretary David Miliband also refused to rule out a military strike but insisted that the international community focus on diplomacy for the time being.

This week, US Defense Secretary Robert Gates played down the possibility of a military option, saying more severe sanctions could help force a change of government in Iran. Sanctions applied earlier were already having an impact in Iran, he noted, with unemployment at 40 percent. If the economy weakens further, he suggested, the government would be forced to adopt new policies.

The goal of the sanctions would be twofold, reports The New York Times:

In pushing for more stringent sanctions, the administration wants to accomplish two potentially irreconcilable goals: forcing Iran back to negotiations over its nuclear program — which the United States and its Western allies suspect is meant to create a weapon — while at the same time winning the support of Russia and China, which are eager to preserve their significant economic ties to Iran.

In a development that will boost US efforts, Russia seems to have reversed course and pledged support for tougher sanctions, with Russian President Dmitry Medvedev suggesting that sanctions should be applied if diplomacy fails.

China, which has the power to veto sanctions, remains opposed, as the BBC reports:

“We believe that sanctions and exerting pressure are not the way to solve problems and are not conducive for the current diplomatic efforts on the Iran nuclear issue,” [said Foreign Ministry spokeswoman Jiang Yu.]