The Obama administration appeared Wednesday to be forging ahead with preparations to attack Syria. It dismissed a Syrian request to extend chemical weapons inspections there as a delaying tactic and said it saw little point in further discussion of the issue at the United Nations.

President Obama said that “there need to be international consequences” for the Aug. 21 chemical strikes he said he has concluded were carried out by the Syrian government.

“I have no interest in any kind of open-ended conflict in Syria,” Obama said in an interview with the PBS NewsHour, stressing that he has not decided to order a military attack.

“But we do have to make sure that when countries break international norms on chemical weapons they are held accountable,” he said.

A closed-door meeting of the five permanent members of the U.N. Security Council, called to consider a British-drafted resolution authorizing the use of force to prevent any further use of chemical weapons in Syria, adjourned without action after Russia and China opposed the measure.

Timeline: Unrest in Syria

Two years after the first anti-government protests, conflict in Syria rages on. See the major events in the country's tumultuous uprising.

In response, U.S. officials made clear they considered such initiatives irrelevant to Obama’s decision on military action. Although officials gave no indication of when a U.S. attack might occur, they said they expect U.N. inspectors to leave Syria on Saturday.

“We see no avenue forward [at the United Nations] given continued Russian opposition to any meaningful Council action on Syria,” deputy State Department spokeswoman Marie Harf said. “Therefore, the United States will continue its consultations and will take appropriate actions to respond in the days ahead.”

The U.S. dismissal seemed to put the administration and its allies at odds with the U.N. leadership. Secretary General Ban Ki-moon, without setting a deadline or addressing the Syrian request for an extension, said it was “essential to establish the facts” and the U.N. team “needs time to do its job.”

Lakhdar Brahimi, the U.N. special envoy for Syria, said international law requires a Security Council decision before any military action. “I do know that President Obama and the American administration are not known to be trigger-happy,” Brahimi said at a Geneva news conference. “What they will decide, I don’t know.”

Administration officials, speaking on the condition of anonymity to discuss internal deliberations, have said that any attack would be of limited scope and duration and would likely target military installations. The Defense Department has positioned warships armed with cruise missiles in the Mediterranean, and Defense Secretary Chuck Hagel has said the military is “ready to go” should Obama give the order.

Russia and Iran, Syrian President Bashar al-Assad’s principal outside backers throughout the civil war that began more than two years ago, have warned of what Moscow has called the “catastrophic consequences” of military intervention.

France, which holds the fifth permanent U.N. Security Council seat, said this week that Assad should be “punished” for the chemical weapons attack.

British Prime Minister David Cameron has also strongly backed Obama’s position on the need to punish Syria for the attack that left hundreds dead, and the two have consulted closely in recent days. Britain’s resolution appeared to have been proposed with little expectation that Russia — which has vetoed measures condemning Syria in the past and this week questioned the attack allegations — would agree.

Cameron also appeared to be running into difficulties at home as opposition grew to British backing or participation in a U.S.-led strike. Cameron called a special parliamentary session for Thursday to make his case and debate the issue. Bowing to political pressure, Cameron late Wednesday also called for a second session Tuesday to provide additional time for debate and a final vote.

The government, Foreign Secretary William Hague said, recognizes “the deep concerns in this country about what happened over Iraq,” when a previous British government, over strong public and political opposition, supported a U.S. invasion based on what turned out to be false evidence of weapons of mass destruction. “We will be clear that we are determined to take action against war crimes” and the use of chemical weapons “on a consensual basis,” Hague said.

In what may mark the closing of the most immediate U.S. window of opportunity to launch a strike, Obama is scheduled to depart Tuesday night for Sweden, where he will spend a day before traveling to Russia for a meeting of the G-20 group of nations.

The administration also hopes to release on Thursday a declassified intelligence assessment of evidence that it says will prove the Assad government’s “undeniable” responsibility for the chemical attack outside Damascus. The U.N. investigators, charged with determining only whether chemical weapons were used, will not assess blame.

“Nobody disputes, or hardly anybody disputes, that chemical weapons were used on a large scale in Syria against civilian populations,” and the opposition does not possess the capability to undertake such attacks, Obama said.

Asked what a limited military strike would accomplish, Obama said that “the Assad regime, which is involved in a civil war trying to protect itself, will have received a pretty strong signal that it better not, in fact, do it again.”

“That doesn’t solve all the problems inside of Syria,” he said. Obama added that Assad needs to understand that by killing civilians and putting neighboring U.S. allies such as Turkey and Jordan at risk, he was “not only breaking international norms and standards of decency” but also had created “a situation where U.S. national interests are affected. And that needs to stop.”

In a letter Wednesday to Ban, Syria accused opposition forces of attacking its military on three occasions this month with a poison “close to what we call the nerve gas sarin,” the lethal compound the United States and others have said was used in the attack on rebel-held areas east of Damascus.

The letter asked inspectors to extend their deadline for departure, originally scheduled for this weekend, to investigate that claim.

In a scornful response, the State Department’s Harf said, “I think this call would have credibility if on day one or two or three or four or five, the Syrian regime had stopped shelling the area that they attacked to systematically destroy evidence, to cover up what they had done, and actually allowed U.N. investigators in.”

“I don’t want to venture to guess why they’re doing what they’re doing,” Harf said of the Syrian government. "But I think it’s clear that we will not allow them to hide behind a U.N. investigation into the use of chemical weapons to prevent any response from the United States.”

The 15-person U.N. team arrived in Damascus on Aug. 18, initially authorized by the Syrian government to spend two weeks investigating allegations of earlier chemical weapons use — two made by the rebels and one by the government. Those plans were overtaken by the Aug. 21 attack, but it was not until Monday that the experts were able to visit the affected area.

On Wednesday, they returned for a second visit to collect samples and interview witnesses.

In addition to the release of intelligence information and coordination with allies, the U.S. timetable for a response is influenced by consultations with Congress. Lawmakers have been largely supportive, but have asked questions about the timing and justification.

In a letter Wednesday to Obama, House Speaker John A. Boehner (R-Ohio) echoed concerns that numerous outside experts have raised about the administration’s assessment of potential post-attack scenarios.

“These considerations include the Assad regime potentially losing command and control of its stock of chemical weapons or terrorist organizations — especially those tied to al-Qaeda — gaining greater control of and maintaining territory,” Boehner wrote.

While outreach to national security committees “has been appreciated,” he said, “it is apparent . . . that the outreach has, to date, not reached the level of substantive consultation.”

White House, Defense Department and State Department officials plan to brief congressional leaders and top members of the House and Senate national security committees by phone at 6 p.m. Thursday, according to a senior Senate aide.

Colum Lynch at the United Nations, Anne Gearan and Ed O’Keefe contributed to this report.