The Senate left town on Thursday for more than a week without reaching a deal to stabilize Obamacare's marketplaces.

Talks between Democrats and Republicans started up again in earnest late last month after the GOP's latest attempt at Obamacare repeal collapsed. However, the Senate left town Thursday without finalizing any deal, although negotiators pledged to continue talks.

Meanwhile, the Senate is in recess all of next week and won't return until Oct. 16, just a few weeks before 2018 open enrollment starts on Nov. 1. A Senate aide said there is "no question a sense of urgency if you want to have impact on 2018."

Sen. Lamar Alexander, R-Tenn., leading the Republican side of the talks, said Thursday that Democrats and Republicans remain in good faith negotiations.

When asked if it was too late to reach an agreement to affect the 2018 coverage year, Alexander quickly responded "no."

Sen. Patty Murray, D-Wash., did not give a timeline for when to finish a deal.

"We are absolutely working on this. No one should think this is easy," she said.

Some senators were perturbed they are leaving for a week without any bipartisan plan.

"I had hoped that we would pass before leaving town a bill that would help stabilize the insurance markets and lower premiums," said Sen. Susan Collins, R-Maine, a major proponent of an agreement.

The basic framework of the agreement is funding insurer subsidies in exchange for giving more flexibility to states for waivers.

The subsidies reimburse insurers for lowering copays and deductibles for low-income Obamacare customers. The Trump administration has been making the payments month to month but has not made a commitment to the payments for 2018, which insurers have been pleading with them to do.

Republicans want in exchange for the subsidies greater flexibility and a quicker approval process for states to waive Obamacare regulations for insurers. States have complained the current process for approving waivers by the federal government is slow and burdensome and they want fewer constraints on what regulations they can waive.

Alexander said earlier this week the two sides have "differences in opinion on what amounts to giving states meaningful flexibility in exchange for two years of cost-reduction payments."

Insurers are already finalizing rates for next year and some could charge higher rates without the subsidies.

For instance, Highmark Blue Cross Blue Shield in Delaware announced Thursday it will raise Obamacare rates by 25 percent next year, according to Delaware Online. The insurer said the rate request was based on the uncertainty surrounding the payments and questions around whether the federal government will enforce the individual mandate that forces people to have insurance.

The nonpartisan Kaiser Family Foundation has estimated that rates for silver plans, the most popular of Obamacare's three metal tier plans, will go up 19 percent without the payments.