As the Obama administration moves ever-closer to a possible military strike on Syria, members of Congress are demanding they at least have a say in the decision -- with some pressuring President Obama to first seek their approval.

It's unclear whether the demands would slow down the administration, as it begins to build the public case for a military strike. One Defense official told Fox News that a U.S. strike is "not a matter of if, but when."

White House Press Secretary Jay Carney stressed Tuesday afternoon that the president has not yet decided to authorize the use of military force. But he made a legal argument for doing so, saying that the United States and 188 other nations are signatories to a chemical weapons convention opposing the use of such weapons, and that there must be a response to a clear violation of those terms.

While officials had indicated the intelligence documents implicating the Assad regime might be released as early as Tuesday, the administration has not yet made them public.

The quickly moving developments, in response to an alleged chemical weapons strike by the Assad regime last week, have lawmakers -- currently on summer recess -- clamoring for influence in a decision that has wide-ranging implications for both the Syrian civil war and the U.S. itself.

Republican Rep. Scott Rigell of Virginia is asking colleagues to sign a letter to Obama that urges him to reconvene Congress and seek approval first for any military action.

Other lawmakers are stopping short of demanding a vote, but still want the administration to bring them into the process before moving ahead.

"I expect the Commander in Chief would consult with Congress in the days ahead as he considers the options available to him," Rep. Buck McKeon, chairman of the House Armed Services Committee, R-Calif., said in a statement, while urging the administration to "act decisively."

Sen. John Cornyn, R-Texas, on Tuesday urged the administration to submit a "detailed plan" on the objectives and cost of any strike.

After House Speaker John Boehner's office complained that the White House had not been in touch, a White House official reached out to Boehner Monday afternoon to discuss the Syria situation.

Boehner spokesman Brendan Buck said the speaker, too, "made clear that before any action is taken there must be meaningful consultation with members of Congress, as well as clearly defined objectives and a broader strategy to achieve stability."

Likewise, Sen. Tim Kaine, D-Va., said: "Absent an imminent threat to United States national security, the U.S. should not be engaged in military action without congressional approval."

Secretary of State John Kerry has been reaching out to Congress on the sidelines.

Lawmakers, in urging the administration to consult with them, point in part to the War Powers Resolution of 1973. The resolution technically requires the president to seek congressional authorization when the military is sent into "hostilities" for anything but a retaliatory attack or formally declared war. But presidents have routinely flouted or found ways around that resolution -- the resolution, for instance, did not stop Obama from teaming up with Britain and France for airstrikes in Libya against Muammar Qaddafi's government.

The Obama administration seems to be waiting for top allies -- like Britain and France -- to get on board before advancing with any plans to attack Syria.

In Britain, Prime Minister David Cameron has called back Parliament to debate and vote on a Syria plan on Thursday. And in France, President Francois Hollande on Tuesday said France "is ready to punish" those who gassed hundreds in Syria.

In Washington, some members of Congress have long been opposed to intervention in Syria. But a number of high-ranking officials are speaking out in favor of a limited strike. Sen. Bill Nelson, D-Fla., was the latest to say a multinational military action would be "appropriate"

Polls over the past year have shown the public is far less interested in getting more deeply involved in Syria. A Fox News poll in July found only 11 percent of voters favored sending weapons to the opposition. Forty-four percent said the U.S. should get out of the conflict entirely.

The Associated Press contributed to this report.